It sounds like they don't just want her on the team for whatever reason. So I think your judgement is correct that they are not planning on moving her back because moving to prep op for one month does not make sense. It would be distracting to all the coaches to move kids in and out of a program like that. Personally I think prep op is a great program, especially for kids with fear issues to be ABLE to progress and compete on their other events what they can without being so constrained by other requirements. I feel some of the comments in this thread are inaccurate about the spirit of the program in that regard. We have looked into the program (it's newish in our state) specifically for that reason, because we feel we have kids who have the ability to progress in competitive gymnastics, just not through the traditional path on all four events.
However moving a kid in and out of a program for a month is obviously not helpful or the way it should be used, in my opinion. That is a more of a distraction than anything.
Realistically you aren't even asking for your child to be moved to a new level. I think once she sees another gym she won't be so scared about the possibility. I don't think any little mistakes are going to make the new gyms evaluate her differently, they will just look at overall ability and strength, etc. To be honest, and I'd rarely make a statement like this, but a kid has straight leg and relatively straight body giants, virtually any gym will put them on L7. I can't really see a reason, as a strictly JO gym, to keep a middle schooler with giants out of L7. Even if she has problems with the other events those should be workable in most cases. My main concern with fear issues is when a kid will never do something, not when they take 5 more minutes to warm up or complete an assignment. That could cause a problem in meet warm up but there are several months to improve that.