FWIW , Stewie has been a loyal, consistent, and star player for USAA basketball since she was 14. USAA Basketball tends to reward loyalty, in part to encourage future younger players to participate. No one should be surprised that she made the team, and deservedly so! Even if it is seemingly at the expense of other players.
Notice that one of the reasons she was left off the team is "chemistry". There has not been a lot of time for the team to practice, so they will be more likely to look for player combinations that work well with one another. If Geno holds to USAA basketball form, he will have two 5 person line-ups that have a lot of familiarity with each other and shuttle them in and out like a hockey line change. The remaining two players fill in on one of these lines on an as needed basis, generally as a defensive or offensive spark plug. My guess for the two 5 person lines are:
DT, Bird, Charles, Maya, and Griner with the second line-up as:
Whalen, Simone, Elena, Catch, and Fowles
with Angel and Stewie filling in as needed.
As great a player Candace Parker is, she doesn't quite fit in either of the two line-ups (except possibly as a replacement for Catch) and might be dissatisfied with being one of the last two off the bench.