Could be as simple as a spot! Could be something embedded in the skin..
It's really hard to see the picture to know what this is for certain. But I can make out that whatever it is has kind of taken a lump out of her ear.
Poor girl! This looks sore. It might be an abscess perhaps (I can't really see)
Has this been going on for a while? Or did it happen suddenly?
I think it might be a good idea to take her for the vet to examine this.