Is she regularly only going to be coming about 15 days a month (even though she`s paying full-time fees) or is December just an unusual month because of Christmas. If that is the case, maybe there was some misunderstanding and she thought that she was substituting the November 30 day for one of the days that she would not be coming over Christmas. Of course, she shouldn`t have assumed that and it`s strange that she would get so upset over it. But I can see how it might be confusing, especially with her first day being on a Monday on the last day of the month. Hopefully after you talk to her, it all gets sorted out and ends up being a good relationship.