I wouldnt change the bit, just use what you usually use. Its a training issue not bit issue.
At the moment i'd just do a bunch of flatwork, polework etc at all three gaits concerntrating on keeping her relaxed. Do lots of transitions with half halts, and changes in tempo within the gaits. Then if you've got that down pat start some cavelleties and gridwork. If she tries to bolt after a jump, make her stop. Stand and relax, then walk on. If you go over a jump, and she doesnt bolt but still feels a little strong, ask for a transition to trot
Theres a bunch of people on this forum that can give you better advice though, good luck!