OMG...that so sucks what's her problem... I think you should say something to your sister in law and tell her don't say anything and take off the day...lol and suprise them in the act..tee hee that's what I would do because I'm sneaky when it comes to wrong doing in our house hold... I'm considered the bully because know one can bully me and if they do they have something coming to them..lol if you need back up let me know..lol good luck