I guess my first question is why was her grip changed. On previous post you had mentioned that Macci had no problems with her grip, so why the change now.
My daughter also plays with a full western. I also had some long term concerns in her using that grip but she hits a good heavy ball and is very good at adjusting her grip to hit slices and low balls. She is currently training under Johan Kriek in Charllote and he has no problems with it. Basically he says that normally he would never teach that grip but if he sees it works well for someone with no glitches that may lead to arm problems down the road then why change it. To twink it in any way would require her to stay out of competition for at least a couple of months so that the change becomes ingrained and therefore she would not revert to old grip, especially under tighter playing conditions. As of now we have no reason to make any changes, she's comfortable with it and so is Kriek. He felt that she drives through the ball very well and the grip did not effect her ability to handle low balls or hit slice FH since she is able to change it quickly without a problem.
In either case, since this is a recent change and she is just aging up to the 12's it does not make any sense to rush into any tournament play at this time. Why risk undoing what the coach has been working on and having her lose confidence in her abilities. Don"t rush things, be patient, keep working on the changes and have it 100 % ingrained. perhaps test it out by playing some lower level tournament where competition is weak but don"t put her in any situation where she may revert, even partially and have begin questioning her abilities.