i'm a groomer, and my advice would be to start her real slow with grooming, like you are
start by brushing her for 10 minutes one day and give her a treat only when you are finished IF she was good. then the next day or so try 15 minutes, giving her a treat after you are done grooming her. and continue on from there getting to longer and longer grooming sessions. but i would reccommend only a treat afterwards to show her she was good but not to spoil her to the point of her expecting treats
those silly dogs sure like their treats haha
what kind of a brush are you using on her?