Some Q's & A's re GP roster
Q: How do you get two (GP events)? A: You skate well enough the previous season (or in summer trial events) to be high enough in the ISU rankings and/or your federation's standings to get invited to GP events . There is no restriction on who can skate at two events -- but for singles, dance, only "seeded skaters" (top 6 finishers at previous Worlds) can get 3 assignments. For pairs, they can have 3 GP events even if they are not seeded skaters.
Q: Why wasn't Angela given the Skate America spot when Yebin withdrew from the event because of injury? A: As others have said, she didn't finish at Nationals because of her shoulder injury; similarly she hadn't competed internationally the previous season (going all the way back to 2002 Nationals, her last major event). Amber was the next ranking skater in the USFSA line-up, so she got the spot. Angela will be competing at Finlandia in early Oct. If she does well there and there is another U.S. withdrawal, she may yet get a GP assignment.
Q: Why aren't Hoffman & Elek competing in the GP? A: Because they are staying another year in the Junior GP circuit -- where they have a MUCH better chance to earn some $$$.
Q: Why does Yebin only have one event? A: She had two, but is out of Skate America because of an (unspecified) injury; hopefully she will be recovered in time to compete at NHK, the last event.