Hmm... That's rough.
She obviously is still in psychosis and needs medication. If she's on it it's going to take time. She's detached from reality right now.
But just because she's sick doesn't mean you can't put up boundaries. You don't have to visit everyday. When I had a severe anxiety disorder a few years ago, the thing that helped me the most was people just treating me normally.
You don't have to humor her paranoid ramblings. It's probably best if you don't, try to change the subject if you can. You'll have to be blunt though, when you're fixated on something like that, social cues don't register. Bring in a simple board game like bananagrams or have lunch and talk about current events or what you're doing (that's not work related).
Most importantly, don't give more than you're able to. It's fine to detach and take a break. If you can't handle being around her, take a break. Mentally ill people are fucking exhausting. It's fine to send her cards instead to let her know you're thinking of her.