Ear sensitivity can be from anything, mites, ticks,burrs, twisting, one too many rounds with an electric fence while trying to get that grass on the other side. Don't be too quick to judge. You'll have to earn her trust and go from there. Approach and retreat are your 2 best tools here. Don't forget to add a good dose of time in there. It can take 6 months plus to get to a point where she really trusts you with her ears. Don't give up and don't give in. Time and patience...all things horse take time and patience.