Try asking if you can have a proper sit down with the coach (or head coach?) so you can "get your head around things". Ask if they can explain how things work over the next few years so you can have this in mind hen budgeting, planning holidays etc. this will help you not come across as pushy/demanding. Let them enlighten you
I get where you are coming from. I think you just need to work out a way of having a proper conversation so you can be reassured it will all work out.
From what you've described, the coach absolutely knows that your DD can do her stuff. There may just not be a place for her in the next group as it's simply too big as you've said. They are probably doing the best that they can coping with the variety of abilities in the group.
Other people have posted about this kind of thing before, you child could possibly catch up with the others later, which is frustrating for now, but think how fantastic her basics will be
Perhaps half of her training group will drop out and she'll have a lovely small group to train with again, with potential for people training different skills.
Of course it would be lovely for her to be training with the higher level. Perhaps she would have been if there had been space, but there isn't. Have you posted about this before? it seems familiar. So at least she gets to be really good and do well competing with this current group.
What are you options?
Talk to a coach and find out what the plan is - if they won't talk then
(If you trust the coaches and the gym, then) close your eyes for a bit, or you'll go mad worrying about it, or
Find another gym.
Wishing you luck. Keep us posted!