Some misconceptions I’ll try to clear up. “She” isn’t making things up, her brain is tricking her that situations and sounds and other things exist and you and most other people perceive it differently. Think of them like optical or auditory illusions. Is it a silhouette of two faces or a vase? Is it a young woman or an old lady in the picture? Is that dress blue or gold? Do you hear, “Yanny” or “Laurel”? or “Brainstorm” or “Green needle”?
Now suppose you look at or listen to the illusion again after a while and your perception changes. Did you make something up or change your mind, or change your story in these cases? Should people be allowed to say you constantly make things up and change your story in these cases? If you see the dress as blue, not gold as your friend does, should she be free to say to others it’s sad and you have a terrible disease? That would feel terribly unfair to you wouldn’t it?
That’s how it feels to be in her position. She’s doing the best she can to understand the world around her, just as you are doing the best you can to figure out what you see or hear when presented with an illusion. And trying to talk her out of her perception would be like trying to tell someone they aren’t sad when you see tears in their eyes— it feels obviously false and invalidating— like you were trying to gaslight their feelings.
Now imagine these illusions were commonplace, say ten percent of the time and you weren’t aware it was happening. That’s similar to her experience. She’s having cognitive illusions instead of auditory or visual ones. If you can start empathizing with her situation, rather than devaluing her by arguing about her being “wrong” for seeing a gold dress instead of a blue one, or try to agree to disagree and let go of black or white (or blue or gold) reality, then you’ll make more progress.
Disclaimer: While I am a part-time caregiver of my brother and father with SMI, I was diagnosed with SZA over thirty years ago. I’m an advocate of appropriate drug treatments for SMI, but I feel they are incomplete treatments and additional CBT, supportive talk and psychosocial therapies are helpful where feasible. Any drug advice is from personal experience or research and not a substitute for qualified Psychiatric care.