It really is the coaches domain. Ideally the coach would take the catwheel all the way back to the beginning. Cartwheel on a line on the floor and slowly move up to the high beam with stacked mats all the way up to beam level.
Clearly if she can do it on the floor beam she changes her technique somewhere on the way to the higher beam, the coach can find out where this is and reinforce the good technique.
The CW on beam looks really easy, but most of the girls are glad to leave it behind, as it's very, very hard.
As to the meet, there is no rushing to get a skill back, so she'll either have it, or she won't. AS a mom all you can do is reassure her and make her see that this is just a CW and not really a big deal. MOre pressure will not help her at all.
SO you could begin by telling the coach that your dd is very upset with losing the skill, and that she is wanting to quit over it. That will open a dialogue where the coach might tell you how they are dealing with it. But to be honest, beyond being a supportive parent there is not much you can do.
One dad at our gym got so upset with his DD losing a skill he was being way to pushy, so I invited him up on the beam to do a few walks, kicks and jumps. You can imagine he was pretty quiet about it after that. Gymnastics is tough.
