My canned (male) response: “I really don’t know her that well. I’m sorry about the situation. Look, I’ve got a telecon in a few minutes. I’ll talk to you later.”
They tend to be wimpy when it comes to dealing with inter-office conflict. Especially if it is between two women.
Not to say that there aren't wimpy female supervisors as well but they are about 50/50 while with guys it is almost 100%. I don't get it. The job of the boss is to keep the group going in the same direction with minimal fuss. But there seem to be few bosses who are able to do that effectively.