Its very tough to let gymnastics be something our kids are in charge of, and not try to fix it all.
My 12 year old DD has been struggling with vestibular issues and puberty and growing for about 2 years now. The first year she managed to compete L7 anyway and placed 3rd at state - but beam was horrific for her - even when she scored 9.5s all season - she backed her series down from BHS-BHS to BWO-BHS, and rarely was able to go for it EXCEPT in competition. She stopped gianting for a while. She lost her full. Her old coach was very patient but also spent a lot of time on the particular skills, rather than just ignoring the issue and moving on (except the giants...which she didn't need because the rest of her bars were so good - now she does though...)
She's 12 now, and quit for 2 months, just conditioned for 2 more, and is now slowly working back up to training for L8 next year. She decided on her own to come back to gym, and she has decided on her own each step. We've done counseling because of the confidence issues, which extended way past gym, and because of some ugliness that happened with some coaches, etc. The counselor does sports counseling, but has let DD decide if she wishes to work on her gym stuff or not (she was a gymnast too...). Dd new gym does a lot of mental toughness stuff and we are lucky to have a very talented mental toughness coach...but again, that's not directly addressing the vestibular stuff/blocks, just the negative feelings, and how the kids can face them....Her new HC was initially super excited to have her on the team, and had her set for L8 with most of her skills ready before DD fell apart - and made the choice to put DD mental health before her teams gymnastics, did not make her compete at the level she had already mastered and consistently placed at, and let her set the pace of what she would train - which has been hard also, but again put DD in charge of her own gymnastics....we recently re-discussed DD and she still feels she is set for a good L8 season next year if she wants it - but HC re-iterated that her first goal is that DD not quit and grow into a healthy, happy young woman. (obviously my goals too...). I think she's about done growing, and her moods are stabilizing some, she no longer says "I can't do those skills" but "I'm not ready, but I will be..." But she is clearly still hesitant, and trying to find her place socially at gym - where she went from a top dog to "what level is that kid doing the strap bar for hours anyway"....
Yesterday at open gym with her brothers she tried a skill she had never been able to do - not a hard one, an aerial, but one that for whatever reason she hadn't mastered previously....and did them beautifully over and over - beam worthy...Her front tumbling is progressing and she's strong again. I think her body is figuring itself out with all the shifts of puberty near done - and if her brain can do the same she'll find there are lots of things that she was struggling with that are easier now....she's working flexibility at home on her own now. Her control is back, she can occ. beat her big brother in a handstand contest - which is quite a feat in our house....
No, she hasn't back tumbled other than a couple of ROBHSBT in months - and on beam only BT and BWO-BHS a few times in months....but she's doing her RO on beam again. She had always planned on going straight to a Yurchenko vault, and did them into the pit beautifully in past - but now she's planning on a piked Tsuk for L8 - because of the back tumbling. She never could do a FLO in past - but now is thinking she'll work that and front twisting so that she has higher level front tumbling to take the pressure off the back tumbling. All this has been her process. Her coach has been putting her with the L7 group (because of a bully in the L8 group) and gave her a list of stuff to work on - checking in with her frequently and helping her with drills for the higher skills - some days she doesn't get much attention and over conditions, but overall the ball is in her court.
All this is to say that yes, this happens OFTEN at higher levels/older girls (perhaps more frequently even). Yes is happens with talented ones. Yes there are almost always social/other kid issues/coach issues that get all wrapped up in the block/vestibular issues. (After all, these are kids...). A good coach will pull back some and let the kid know they are valued as the person they are, not the skills they can do. A good coach will also walk the balance of finding ways to help the kid progress as a gymnast even while struggling - and this will be different for each kid....as parents we can do a lot by making sure our kids are getting the positive encouragement they need, letting them know we have confidence in them and that this is not their fault. We can look to mental toughness/counseling as a support for our kids WHILE they go through this - but we can't push them through it, we can't fix it, etc. And in the end, as DD HC says, they need to be doing gymnastics if they "love doing gymnastics", otherwise they are done. But they aren't "done" just because their body won't do what they want it to do right now (in this case their brain...).
From my reading of past posts - months to years is NORMAL if the issues really are vestibular. Its hard to say - my DD can actually describe seeing stars at times, and feeling like she doesn't know where her body is in space (even while executing perfect skills) - luckily she has the muscle memory of doing many of these skills so many times before this became an issue - she's not worried about getting hurt, nor am I (more than the average L8 mom). Time off gym was really hard for DD and for me - she had been doing it so long and it really was a big part of her identity. But it did help her see that she wanted to go back, and put the ball in her court. She had pushed through things the year before FOR her old coach - she misses that kind of personal attention (that coach was extremely hands on, and in my opinion too close to the girls) - but her new coaches are nothing but helpful and they do believe in her - they just want her to find her own intrinsic motivation - something we all need in life.
The only thing you can do for your DD is support her, let her know these issues are a normal part of most girls gymnastics journey, that it doesn't mean anything about how "good" of a gymnast she is, and that if she loves gymnastics then she should do gymnastics....if her coaches are making this into an issue that will come to be her identity (DD felt that she wasn't a good gymnast anymore because she couldn't MAKE herself overcome this - old coach spent a lot of time telling her not to "let this skill defeat you"...she took the blame on herself rather than realizing it was a physical thing she had to be patient with) then you may need to try to see if there is a way to get everyone on a more supportive page - BUT keep in mind that if the coaches seem to be spending less time with her it may be for the RIGHT reasons - giving her time and realizing that this isn't a quick fix situation. Communication with the coaches is really important - I don't watch practices much at all, and only check in with DD coach every month or 2 about this - but it does help when we take that time to see that we are working together to support DD in her journey.
Oh, and yes, its tough as a parent to see them struggle - and all the hopes we have for them come into question. Its natural to want to fix it. I ache to see her team mates competing easier L8 routines than she did as a L7 while she is doing V-ups in the corner by herself...but that's what friends and internet forums are for....we must keep it to ourselves and just be there for them. In the end how they feel about themselves is far more important than what level, skill, etc they got to in gym!
and it's free. 
