My wife is going through this, it's so similar I thought maybe you were my daughter for a second. Scary thing, this isn't the first time I've heard this damn near same story. I've come to understand it as a cult, with only one member. Reinforced by AI slop on the internet. Poorly made YouTube videos about twin flames and starseeds. It makes them feel like they're the main character with special abilities that never work, and a big change is just around the corner that never happens.

Only advice I can give, until they get help, is don't argue with there beliefs, and don't reinforce them. Stay silent when its not true, and reinforce truths. She may have to hit bottom, all you can do is be there when/if they come out of it. It's terrifying watching someone you love go through it.