Thanks everyone. I know it's too late this time to say anything, but as this is not the first time my brother has pushed me to include her, I was looking for phrases for the next time. My brother actually met my SIL through me. When I met her, I was a teenager. As I've gotten older, her behavior, her dress, her maturity, nothing has changed. When I talk to her, its like talking to a teenager. I've seen her pitch fits like a toddler. I just lead a very different life, I work, I'm into fitness, we just have nothing in common. Plus, there have been several times her behavior has been completely unacceptable, and while my brother may forgive and forget, when it affects other family members (like driving blitzed out of her mind with my niece in the car, in which she hit and damaged property and then drove off), I'm not as quick to just sweep it under the rug as he is. Then I'm the villain because I refuse to take her anywhere alcohol is involved. After that incident, it was about a year before I would even speak to her again and only because she had stopped drinking.
If it wasn't for the fact she was my brother's wife, she would have long since faded away. As for brother, he will get over it and hopefully before the slew of family/holiday events coming up. I just do my best to try and stay away from the entire situation but my brother does his best to involve me in it.