She could have ear mites. The inside of her ear would look like black crumbs. You might think it just looks dirty. She might have been bitten by a fly or mosquito. Examine her all over her head. She could also have a tick. It needs to be removed oh so carefully, because it's easy to snap off the body and leave the mouth parts in there. I bought a little tool from the vet to remove ticks. They need to be removed in a circular action, because they go in in a circular action. If you pull it straight out, she will have a huge crater. Don't do that to her. She might have allergies, or even recently developed allergies. Google "pet advice free" if it's not any of these things. I see lots of sites there.
Ear mites if you use a q-tip lightly and there is brown ear wax wipe on white paper if you see black specs moving chances are ear mites. Many pet stores and even Walmart carry drops to kill them and if it continues see a vet
Check inside. Is it dirty? Roll us some cotton or a damp paper towel and gently clean the dirt. A visit to the vet would be good. My dog has food allergies that cause her to get ear infections. Better to consult a pro!