Personally, it took me forever to teach my mare her turn arounds! But once she got it, she got it for good!!! It's all about your foundation. Don't be worried that she is regressing. That is normal, I see it as her learning. Process of elimination for what you don't want. I think you first need to make sure her front end is correct and she is crossing over right. Instead of sucking back and losing her frame. I trot lots and lots of tiny circles. Some small that my mare really has to get the front end foot work down (most important part of the turn around.) When she is soft in the face, neck, shoulders and legs, I let her trot into a spin. The moment she flings her hip out (not talking a little, talking about moving completely sideways) I would push her back out into that small circle from hell. Softness again, let her come into the turn, get a few good cross overs and stop. See, for my mare, correct turn arounds are a reward. The small circle is WORK!!! Be very patient, this is a tough one for some horses to get, but you have to teach them right and reward them!! Could it be that you pushed her too fast too soon and lost all of her confidence? If so, then start back over with slow but correct turns. Hope she is doing much better now!!