To be clear, the plan I am thinking about is:
1. File I-129F, she waits for the visa outside of the US.
2. Once she gets the K-1 visa, she enters the US at SFO (this is the single entry, 90 day clock starts then).
3. A couple weeks after that, fly to St Thomas.
4. Wedding
5. Fly back to California.
6. File AoS, Advance Parole etc.
7. Wait for GC
So, my questions are -- for step (3) of the plan above, is flying to US VI (directly) considered an intra-US flight? I think there's a customs check in US VI but not an immigration check. And for step (5), are there immigration checks on coming back from US VI?