Hi Lani,
I couldn't find any information online that could tell me what is wrong with your squirrel. My only thoughts are that she may have irritated it somehow. Maybe by rubbing it on something. I would suggest that you watch her over the next week to see if she starts acting funny and if the redness gets worse. If yes, I would take her to see a veteranarian. If not, I am sure that it is nothing to worry about and that she will be ok.