Times like this call for sharper shorter aids. If she takes a long time to respond, you sometimes need to give her a sharper tug to get a quicker response. But in doing so you need to release a lot faster and not just sit there holding her mouth. That’s when horses tend to ignore your hand and keep going. Try a few short tugs with your reins and the minute she comes back release and give her a pat. If you are trotting do lots of trot walk/trot halt transitions to keep it interesting. Remember stopping comes from the leg not nexcessarily the hand, so if you have a good trot where she’s working from behind, you’ll find stopping much easier with these short tugs. You’ll find her responding much better after. If she also opens her mouth a lot, try a loose flash noseband to help her stay in contact with you.