I know that if I have a really snotty nose happening, I often get sore ears due to the mucous backing up in my sinus cavity.
Try getting her to lie on her side with the sore ear facing up, if this relieves the pain, then you know that's what it is. If that works, maybe try an antihistamine to dry up the mucous or get her to drink tons of water to make sure that it stays runny, not gluey and thUs drains better.
Best of luck, sick kids are so sad to watch