This must be a bit of a dilemma for anyone trying to care for someone who has auditory hallucinations and is almost constantly engaged in conversations with figments of her imagination. For instance, very often and almost always when I'm trying to get S to do something she will suddenly announce,, 'She's gone!' and sometimes get very distressed. I can either ignore this or try to reassure her. But I can only reassure her by to an extent playing by her rules and at least briefly accepting the reality of her universe. My rational self tells me that there is something wrong with this. But sometimes I cannot stand listening to her distress. I'll ask her, 'Who's gone?' and she'll reply, 'Micia' (the name of one of her 'friends' - named for a cat that we used to look after). I'll say, 'Don't worry, she always comes back.' because she always does. I don't know if this really helps S but sometimes it seems to and my concession to her distorted brain is a small price to pay.
There is something called validation therapy which, as I understand it, involves entering into a person's imagined universe in a big way and 'validating' their experience and perception. I'd be very unhappy with that - and I'm sure I'm not alone - as I instinctively feel that it would be better if S spent less time in her universe and more time in the 'real' one. And of course there's an approach that tries, probably with people at an earlier stage of the condition, to reorientate people to reality by, for example, putting great emphasis on the date, day of the week, time etc. This is called, unsurprisingly, reality orientation.
As usual, it seems to be a question of balance and going with your gut feeling. So I am getting used to sometimes entering S's universe, usually to reassure her, and sometimes trying to get her to understand the real world again, usually when I need her to do something, or when I need to do something for her that requires her co-operation. Once again, I count myself lucky that I can usually get her to 'snap out' of her imagined universe long enough to get things done, though often, as with eating, there's an almost farcical stop/start sequence involved.