After watching this movie, here's what I think:

Estrella's mom, in real life, was cheating on the dad, and Estrella either knew about it, or she maybe had actually seen it (like that scene in her "dream" where she sees her mom with the guy). So, if the whole movie was a dream or fantasy, I think that would be why Estrella included stuff about her mom sleeping around. Also, if the mom was actually having affairs with the teacher and the security guard guy, then it would make sense why Estrella would imagine the vampire (her dad) killing both of them in her "fantasy."

Adding to that, I feel like the dad, in real life, was either abusive towards the mom, or he was abusive towards both the mom and Estrella. In Estrella's "fantasy," she depicts her father as a "vampire," and he is also a violent killer and abusive towards the Mom. Maybe there was sexual abuse going on as well, based on the scene where the vampire/dad tells Estrella to give him a kiss; I'm really not sure though. But, the dad was depicted as being extremely violent, so there had to have been some connection between that and the way he was in real life. Plus, why else would Estrella envision him dying in such a graphic way? Punishment for what he had done to her and the mom?

I think Estrella's fantasy also showed how she wished that she had a better relationship with her dad. The part where she excitedly shows the "vampire" her Nosferatu doll and also her school pictures is an interesting scene, and I think it illustrated how Estrella wished she had a close, normal relationship with her father.

The only things I can't really make sense of are the mother's past and the whole thing about pretending her dad was dead. Also, I didn't quite get how Estrella's fantasy related to the movie she was watching. I guess maybe I missed what that other guy (the one who got electrocuted) had said to the mom when he spoke to her at the hospital? I didn't understand how the guy from the movie fit into the plot of Estrella's fantasy.