It's hard to say. I'm sure all junior eligible girls are asked at the beginning if they plan on competing as a junior or a senior next year. Once that is confirmed they start monitoring girls in the summer competitions. Last year the highest scoring girls were chosen to compete on the JGP aside from Kaitlyn and Starr.
Starr was injured early in the season and wasn't able to score well until September. Kaitlyn wasn't age eligible. This year they are the reigning junior gold and silver medalist, so they will both be eligible for slots.
The reason the ladies did "badly" was due to inexperience. Ashley and Alexia just came up from novice. First year juniors ladies seldom do well on the JGP. Brynne was 17 and body changes caused her to start underrotations. The tech controller didn't call her on her jumps at skate Detroit, so she didn't learn of the problem until the JGP and by then it was too late to fix it. Tessa was recovering from an injury. Gabby was a last minute replacement, she only had a week to prepare. Vivian Le was supposed to compete but was injured.
USFS wanted Tessa and Vivian since healthy they would've scored fairly high. But that didn't happen, so they gave slots to girls that had some potential, with no expectations of winning. Of course it's bothersome to see us not winning any medals, but last year doesn't bother me. I call it a recovery year. In college basketball you have off years when a bunch of players have gone pro and your new players need to build up their skills to compete. I'm more optimistic about next year. But I wait until Broodmore to make a solid prediction on who will get slots and how well they will do.
Yeah but US Junior Ladies have been getting worse over the last 2-3 years which isn't good. Not winning a medal at all is worrisome to say the least. Kaitlyn does seem to have some potential but will she suddenly have a big growth spurt and can she rotate her jumps is the big question.