How old is she? Is this her first wheel? Sometimes when you give a young chin a wheel they over do it at first, especially since you should wait until they are full grown before giving them a wheel. You may need to just let her use it when you are there to watch her and take it out when you aren't there, so you are there in case something goes wrong. My guys did fly off their wheel a couple times when learning (not a chin spin but their first wheel was a drum style like that), but it only took a couple times before they learned how to slow down and get off properly.
If she is at risk of hurting herself and isn't learning you may need to just remove it. Other then that you can try to make sure there is enough padding so she doesn't get hurt. Chins don't need wheels, just like kid doesn't need a swing set, they are just nice to have.