Spoilers:
I don't remember the episode, but it's shown in a flashback. Shes killed when Miles (being possessed by Quint) pushes her down an empty well.
Just before Dani arrives at the manor, which is why Hannah seems a bit confused when she welcomes Dani.
The ghosts are still able to interact with the real world. Otherwise Viola couldnt leave muddy footprints, or kill people.
And the faceless boy couldn't move the dolls and so on.
It just takes some practice as Quint finds out when he's killed.

@SolarPowered said:

Spoilers:
I don't remember the episode, but it's shown in a flashback. Shes killed when Miles (being possessed by Quint) pushes her down an empty well.
Just before Dani arrives at the manor, which is why Hannah seems a bit confused when she welcomes Dani.
The ghosts are still able to interact with the real world. Otherwise Viola couldnt leave muddy footprints, or kill people.
And the faceless boy couldn't move the dolls and so on.
It just takes some practice as Quint finds out when he's killed.

Right that clears up a whole lot....thanks !!!!

I didn't watch the entire series - it was too PC for me. But I watched the beginning and Hannah Grose was a ghost from the start - it was telegraphed by the fact she always refused food and drink. As usual inferior writers decided that they were far better than a classic author and turned "The Turn of the Screw" by Henry James into a mish mash of unrelated stories. The original film "The Innocents" told this story in a far better way.