Talk with her. Make sure she understands you are training for dressage not event. See how much experience she has with dressage. Carefully explain that although you feel you could possibly learn from her, you and your horse were uncomfortable with her during your first lesson. She may have been testing you although since you are paying her she should really play those kind of games.
But if you don't feel comfortable just talking with her about riding you definitely aren't going to do well taking lessons from her. If that is the case get another trainer who specializes in dressage and use that as the excuse for not training with her.