it sounds as though she is sour. have you taken her on a trail ride to get her to relax adn be happy ? What are you schooling her in ? is it causing her pain ? example jumping fast turns ? hard arena landing ? going into a fence crooked not setting up correct ? or if , reining, sliding , stopping turning fast could all cause pain and grumpiness . You may say you are soft on the bit, but do you have to much pressure, to little pressure ? bit setting in her mouth correct ?
saddle pad not clean , something poking her? same for the cinch/girth ..