That's great news, Amy. I really do believe everyone, including the humans, are happier now that she is segregated. Yes she is alone, but cats are loners sometimes (she definitely was) and she did not get on well with the other cats. She is so unbelievably loveable now, whereas before she was very standoffish and would growl the moment you petted her a little too long.
She still cries a bit at night when she hears my voice, but that stops and is nowhere near as long and persistent as it was for the first 4 weeks she was in the room. She runs back to her room, as if to protect it, if the other cats come up the stairs to see what the fuss is when it's just she and I upstairs. She still growls at the other female, but the relationship between her and my male has seemingly improved. She tolerates him when he comes on the bed to visit, but will not tolerate it if my other female visits.
The change is quite remarkable now that she's had time to settle in and get used to it - and my house is smelling a lot better!!! The other cats are back to being frik-and-frak together, sleeping curled into eachother, walking around purring again, and generally are back to being my babies.
I am so glad to hear that this can be a long-term solution.