Liz - Molly doesn't like the other cats, she has been with me 17.5 months now though, so not one of the newcomers, and she does have food, water and litter tray in my room so she doesn't have to compete with any one (she doesn't even have to move off hte bed to eat at times, I do pander to her quite a lot!!). She has been downstairs more since she went to the vet though, maybe she is expecting me to do something (which is right, she needs worming!!), and for the first time in a long while, I am going to shut my bedroom door tonight so that no one can get in and upset her, as Pumpkin does keep sitting on my bedroom floor and ignoring the growling and hissing. It isn't related to her not eating though, as she happily eats dry food, but she was a bit dehydrated over the weekend after only eating dry, so that isnt the solution either.
Hairballs and constipation do seem more likely, she is just a nightmare to get anything other than LActulose into though.