copying bad behavior

doodlemonkey22

A few months ago my SIL moved to our city. So naturally our kids started  hanging out more often. Before this we only saw each other once a year. I had heard that her DD has some behavior problems but I did not know the extent until I started seeing her on a regular basis. She is 8 and my DS is 4. She can get quite nasty. Mind you she's at our house playing and she'll forbid DS from entering his toy room and forces him to watch her play with his toys. She likes to instruct him to lose when playing games so she can gloat about her victory. If DS is playing with a toy she grabs it out of his hands and says "you're playing with it wrong. let me show you how to play with it." I could go on. Obviously I don't put up with the behavior at our house. Whenever she's caught red handed she turns on the water works and has some excuse. SIL doesn't think her behavior is a problem and that it's normal. Is it? I don't have girls but that don't sound right to me. Anyhow the major problem with this is that after spending a day with her, DS copies the bad behavior with his little brother. I just don't think this behavior is appropriate. It takes 2-3 days of constant time outs to get it out of his system. I just don't know what to do.