I guess we will never know, if it happened when she was chilling alone. But the two prophecies we know she made were made when there was just one other person in the room. Maybe the gift she has senses this and the prophecy only comes out when there is someone to hear it alone (or alone as far as she can see)?

It is not a big dataset, but it is a pattern.

I can't answer that by while we're on the subject, is the consensus that she was legitimately gifted in a way that is unusual for any regular magical person or was she just having seizures and unintentionally parroting stuff, I can't remember altho I loved her casting and rooted for her even though I though she was full of shit. Edify me if you can

Edit: I will point out that I think her character was influenced by Greek priestesses that unknowingly probably were inhaling deliriant or dissociative gases because the temples were in mountains that was presumably wafting up and intoxicating them, making these kinds of ecstatic states more likely. Take from that what you will, it never really talks about if they saw indicia of drug use but maybe there's a sharper eye who can dispute this idea

Edit: doesn't she burn incense or some shit? I feel like there was a smoky atmosphere in the moving picture version

She predicted that I'd reply here actually.

She makes seemingly random guesses that come true iirc right?

Most of the predictions she makes in the books do come true, she's just clueless about the context of any of it. I suspect dumbledore keeps her around in the castle because she does see from time to time. He's likely more concerned with keeping others from hearing them than hearing them himself.

Yes, why not? Outside of what’s written in the books, as long as the author doesn’t write something that contradicts it, you can speculate and imagine as much as you want. Only the author can give you a definitive answer.