She's not bipolar. I don't know family history other than her brother is an addict and her mom posts 20 political memes a day on FB that venture into conspiratorial stuff (but that describes a lot of people I know).

The only signs we can come up with were a few times going back 20 years, either at a party (drugs) or a canoe trip (drugs) where she thought people were talking about her/plotting against her. I wasn't on the canoe trip, but I always believed her that some people in another group of friends we know were mercilessly cruel to her. Now I tend to think it was a manifestation of whatever this is.

Other than that she's been one of my most solid friends and always had her shit together, very successful career, someone I would call when I needed life advice, etc.

I know someone who had a lesser but similar episode after taking shrooms for the first time. It was about a week of paranoid delusions (The Truman Show came up a few times). After he snapped out of it, he totally turned his life around; went from a very phlegmatic personality to totally type A, got his degree, and now owns several businesses. The human brain is just so complex.

That's uplifting to hear. So far my friend has seemed more or less okay for a couple months. Fingers crossed. I honestly had no idea if these things could just go away on their own. It sounds like it's possible at least.