i have the same problem with lady she will pay attention to jason and to me. Our trainer suggested that it's because i do a lot more for her feeding and spending more time with her in the day she doesn't respect me. Not sure how much truth there is in that though! I think that lady pays more attention to jason because he has a stronger toned voice and since i started to do raise my voice a little lounder she does the commands for me as well. Also try using her fav food we use little bits of chicken in training when we want her to work hard and normal treats through the day in training sessions. i also praise her like crazy when she listens to me everyone in our puppy class thinks that i am crazy when i jump around because she listened to me. Hope that helps.
Natalie, mummy to lady (blen) 8 months old