She was very necessary.

She represented the (one possible) future for John.

She was (in her mind) a faithful follower of his (and still is).
So much so that she was willing to lose herself to get him back on track.
Willing to get a girl killed (sacrificed) to save humanity.

Jesse was a consequence of the road John was headed down.

She was the horror of the future.

John's own people mutinied against him and Jesse was actually one that stood up for his cause, but eventually sided with those who turned against him (in a way).

The terminator known as Cameron was continuing John's wishes (he was dead, I think. Cameron accidentally killed him).

John became a terminator lover (in a way) and Jesse needed to get him back on the track she thought was right.

And what's wonderful is that we eventually find out what happened with her and understand where she's coming from.

She's not some 'villain', she's human with a side, with many sides.

And her actions were understandable, though lost, just as she thought John was lost, off the right path, whatever that may be.

For the time-travel/mythology aspect, we had someone who had a slightly different future from Derek, proof of alternate timelines.

For John, Jesse was the horror of his future: how terrifying it must be that his own people turn against him, that he can't trust anyone, and most importantly, not even himself.

Jesse was John's doubt about his own self.

She was the ghost of his future: Hopelessness.

Jesse's purpose/mission was to get John away from "her", from it, from them.

And she succeeds.

Derek was already a reminder from the future, a hint, that John sided with terminators and that could be dangerous.

Jesse really pushed that point across to John.

John realizes that he has gone too far in one direction and needs to side a little more with humans, to not be too trusting in "them" (terminators / Cameron).

When John is taking this all in (a 16 year old), he sits between his mother (human) and Cameron (terminator).

He collapses in anguish towards the human side, taking comfort in mother (nature), the mother of the future, the mother of humanity.

TSCC was brutal and truthful, not some fake bullshit.
That's why I loved it so much.

We explored John contemplating and attempting suicide in addition to many psychological aspects of trauma and life.

@Xyberfaust said:

She was very necessary.

She represented the (one possible) future for John.

She was (in her mind) a faithful follower of his (and still is).
So much so that she was willing to lose herself to get him back on track.
Willing to get a girl killed (sacrificed) to save humanity.

Jesse was a consequence of the road John was headed down.

She was the horror of the future.

John's own people mutinied against him and Jesse was actually one that stood up for his cause, but eventually sided with those who turned against him (in a way).

The terminator known as Cameron was continuing John's wishes (he was dead, I think. Cameron accidentally killed him).

John became a terminator lover (in a way) and Jesse needed to get him back on the track she thought was right.

And what's wonderful is that we eventually find out what happened with her and understand where she's coming from.

She's not some 'villain', she's human with a side, with many sides.

And her actions were understandable, though lost, just as she thought John was lost, off the right path, whatever that may be.

For the time-travel/mythology aspect, we had someone who had a slightly different future from Derek, proof of alternate timelines.

For John, Jesse was the horror of his future: how terrifying it must be that his own people turn against him, that he can't trust anyone, and most importantly, not even himself.

Jesse was John's doubt about his own self.

She was the ghost of his future: Hopelessness.

Jesse's purpose/mission was to get John away from "her", from it, from them.

And she succeeds.

Derek was already a reminder from the future, a hint, that John sided with terminators and that could be dangerous.

Jesse really pushed that point across to John.

John realizes that he has gone too far in one direction and needs to side a little more with humans, to not be too trusting in "them" (terminators / Cameron).

When John is taking this all in (a 16 year old), he sits between his mother (human) and Cameron (terminator).

He collapses in anguish towards the human side, taking comfort in mother (nature), the mother of the future, the mother of humanity.

TSCC was brutal and truthful, not some fake bullshit.
That's why I loved it so much.

We explored John contemplating and attempting suicide in addition to many psychological aspects of trauma and life.

Outstanding analysis. Thanks for posting this.

She was also a key factor in demonstrating the idea of alternate futures. Her memories of the future were different from Derek's, which was significant in demonstrating that they were in fact changing things.

Recently rewatched and studied the series carefully. I believe Jesse was from the same timeline as Derek. I think Derek really did block out what happened to him when it came to Fischer.

We never ever see, in the entirety of the Terminator (live-action) series, any evidence that time-travelers from the future are from different time-lines. We never see TWO of the same persons from different futures. We never see any other time-traveling version of the same time-traveler from the future. It's always just ONE version from the future in every unique timeline. The only exception being the Skynet entity in Terminator: Genisys, revealing that it went through many timelines, which makes total sense because it's computer information that can be transferred from a terminator chip going back in time and copying itself to future terminators with the help of CyberDyne (or whatever company building A.I.) advancing that information on to new 'bodies', allowing it to always reach the future and always go back in time to the next clean-slate malleable timeline.

Jesse's and Derek's past(s) (all their flashbacks) are identical (they match up) with the exception of the memory of Charles Fischer in Derek's mind and, supposedly, 'Billy Wisher' in Jesse's mind. In the scene where Derek mentions Billy Wisher to Jesse, it's unclear what interactions Jesse would have had with Billy/Andy if we do suppose they came from the same future.

Derek and Jesse first meet AFTER Kyle jumps back in time, which is AFTER Derek is tortured in that basement and finds out that Billy Wisher is actually Andy Goode. So, would Derek, in the short time he knew Jesse, ever mention "Billy Wisher" when he now knew him as Andy Goode and is planning on killing him? I don't think Derek would bother introducing "Billy Wisher" to Jesse after all that, after he knows there really is no Billy Wisher. Derek kept Billy Wisher/Andy Goode a secret from Jesse when he said goodbye, going their separate ways on their separate missions (Jesse on the Jimmy Carter submarine and Derek going back in time to fix all the mistakes, which was primarily to kill Andy Goode). Derek didn't tell Jesse (in 2027) his mission was to go back in time and kill Andy Goode. Just as Jesse didn't tell Derek (in 2008) that her mission was to get Riley killed. Jesse didn't even let Derek know she knew Riley. Derek hid his secret from her to stop the war (killing Andy) while Jesse hid her secret from him to win the war (killing Riley, via Cameron, to get John to leave Cameron).

Between Derek, Jesse, and Billy/Andy, they were rampant liars (to everyone, including each other). Sometimes they were honest with each other, but most of the time, they always had something to hold back, something to hide, always on some mission, usually personal.

Derek asks Jesse what date her Judgment Day happened. She doesn't answer. Why? She was keeping secrets from him. She was keeping from him the whole plan she had. Jesse wanted him to think they might be from a different timeline so she would never have to answer his questions, because what's the point if things are always changing, which is what she then states to him. And what's the point of answering any of his questions if they come from a different past. Because if she did answer with the truth, it would be the same date, and he would then ask more questions, which would have to line up with everything he knows (from THEIR past together). If she gets him to think they are from different pasts, none of her answers have to line up with his memories, and if that's the case, then no point in answering or explaining, because how would he then understand where she's coming from. It ultimately backfires on Jesse though. This secret keeping and playing coy, lying to him, ends up giving Derek further allowance/justification(in his mind) to kill her if she's not his Jesse.

Even in their last moment together, she doesn't spit out what really happened (the loss of their child), she just listened to Derek talk about his reasoning for killing people he loves. And when she tried to talk, Derek refused to listen: "Derek..." "Shut up." "...please..." "Shut up." Earlier in the convo, he answers for her - (here's whole convo) :

"Derek..."

"Do you know who Billy Wisher is?"

"Who?"

"No. No, you don't. Where you come from, he doesn't exist, he never did. Billy Wisher was my best friend. He was in my squad, we fought together. We saw things you can't imagine. He was like my brother and I loved him. But it turns out I never really... knew him. His real name was Andy...Goode. And back here in this world he created a computer program, a program that becomes Skynet. So Andy Goode is dead. And Billy Wisher is dead too. Because I killed him. I came back here and I killed him. He was my brother... and I loved him and I killed him. And I did it for Kyle... and John, and I did it for you."

"Derek..."

"Shut up."

"...please..."

"Shut up."

"You have no idea. You have no idea what they took from us."

"Stop it, just stop it. I don't even know you. I don't know who... you are."

"I'm Jesse! I'm Jesse!"

"You're not my Jesse. You never were. John Connor said to let you go. I'm not John Connor."

In this moment, Derek knows and has decided he is going to kill Jesse. Derek, in his mind, has to make sense of this action and what better way to make himself feel better about it than to say that she's not his Jesse. So, the first thing he says is, "Do you know who Billy Wisher is?" And she doesn't. Deep inside, he knows that fact, because he never introduced her to "Billy Wisher", if to Andy at all. "Who?" He then answers for her. He has to justify her murder in his mind.

If you're now wondering if Derek really killed Jesse (which is what my whole argument of Jesse not knowing Billy, and the reason for Derek to bring him up, hinges on-though it's the intent that matters), consider the conversation he has with John Connor right after. Derek says Humanity rises or falls on John's shoulders and they're always watching John.

"For me to make a mistake?"

"For you to be human."

John then asks Derek if he killed Jesse.

"John Connor said to let her go."

Which was the human decision to make. But letting Jesse go would also have been a mistake (in Derek's mind). Derek is not looking for John to make a mistake, he's looking for him to be human. Derek is here to "fix all the mistakes" (which he told to one of his buddies before jumping back in time).

In the next episode, Derek seems to acknowledge the fact that he and Jesse were from the same timeline when Cameron (obviously from the same timeline as both Jesse and Derek) shares that Jesse was pregnant and lost the child. Cameron remembers that (from Jesse's flashback that we see) and Cameron arrived before Derek killed Andy Goode.

We never see Jesse hanging with Derek's gang in either of their flashbacks. And EVERYTHING else matches up between them in memories (besides Fischer). EVERYTHING matches up between all other time travelers in every unique timeline we witness (in each film and TV series). Derek's clouded memory is the only thing that leads to this possibility of getting visited by time travelers from different timelines. There's no other evidence indicating that possibility.

Derek's mind is damaged, kind of like Cameron's chip. Disassociation, much like Cameron forgetting who/what she is (in Allison From Palmdale), is due to extreme trauma to one's mind, and a coping mechanism.