*Spoilers* The end to the ending debate.
***Spoilers***
I know a lot you have been debating on whether or not Florence is dead at the end. After watching this movie about 3 times in a row, I can say with 100% certainty that Florence DID die. Here's why...
1) At the beginning of the movie when Florence first comes to the house, she encounters Tom who says, "Hello" and she acknowledges his greeting. At the end of the movie, she does the same thing to the lonely red-headed boy, Larry. Directors often like to use this linking mechanic to indicate similarities in occurences.
2) Maud dies rather quickly after drinking the poison, but Florence lingers a while longer which may have you thinking she didn't drink enough, but if the poison is already having an effect on her, ie: room spinning, loss of consciousnesses, then that indicates that the poison has already entered her bloodstream which would make vomiting pointless.
3) Florence tells Tom, "I can feel you now." as she lays on the floor dying. This, to me, says that she can't see him anymore, but she can feel him there still. In general ghost lore, spirits usually can't see each other unless they've died together at the same time. This also plays into the end when she tells Robert, "Not being able to see them isn't the same as forgetting them."
4) The headmaster. He says they'll tell the boys that "it was an unfortunate accident." and proceeds to berate Florence's abilities even when she is right there. Even in 19th century etiquette, a man would not dare to insult a woman in her presence. She even walks directly in front of a man who completely looks past her.
5) The cab. Florence tells Robert that she will walk to the cab. She then turns around and walks back towards the school. She is now bound to her ghostly home, forever. Robert looks on in sadness.
6) Interacting with objects. This shouldn't even be an issue. Tom touches and moves several objects around the school and it shouldn't be a surprise that Florence can as well.
7) The clock. When Florence is lying on the floor, dying, the clock is heard ticking. When Robert enters the room, he looks on and the clock stops ticking. Florence's time is up.
8) Robert. I think that Robert might've killed himself upon finding Florence dead in the kitchen, which would support the ghost lore of ghosts only being able to see each other when they die at the same time. He seemed like an emotionally unstable person to begin with. He was self-harming, probably suffered from PTSD, and started going bonkers when Florence was poisoned. He seems unusually calm and put together in the last scene. Although Florence and Robert were going to "take a cab somewhere", neither of them are seen doing so. Florence walks back to the school (probably because she is bound there now) and Robert just stands there looking on. Is he sad that his ghostly lover cannot roam as freely as he? Is he also bound to the school since he died there? Nobody acknowledges Robert, not even Larry the lonely red-head. Does Robert know they are dead and Florence doesn't? This theory doesn't have a lot of grounds, but for me, it's in the air.
As for everything else, I'm very certain that the intent of the directors was for Florence to be an unsettled ghost. The overall theme was melancholy and I don't think that after Florence's grand plea to live, while on the verge of death, she would be granted with such a great escape from her fate. The end is supposed to be tragic. The entire story is tragic and now, Florence is another piece of that tragedy.