I agree with horsesaremypassion. Look for anything that has changed since the new behavior.
Another thing is getting a good routine set in to calm her.
The other thing is the playful game (many videos of this on internet), to learn how to get her attention before. I was actually thinking of doing a video on how to use a plastic bag and making her back up to it.. If you have a buddy to help you its even better.
So have the buddy with the plastic bag on a stick, standing 10/15m behind her. Start on the ground.. The bubby starts wooshing the bag, and backing off when shes "really" scared (so on the first one he will back up right away, then get more sensitive to how "jumpy" she is), the horse has to follow while backing up.. What you are looking for is the head to come down. then stop, say a loud "good", and your buddy will stop at the same time.. do this until you can back her up all the way to the bag touching her (be careful for kicks buddy).
Then do that also while riding.
If you don't have a buddy, use a windy day, and tie the plastic bag to the fence of the arena or safe enclosing.
Be careful to getting "run over".. To control her direction control her nose like the rudder of a boat..
After this you can also train her to let herself be run up to..
Hope this helps,