Wow, you have some control not to give her notice immediately!

I had a dcb recently who was quite abusive to my sons as well. Thankfully the parents backed off before I did, but I was ready to term him. The way I thought of it was "if he hit/bit/hurt one of the other kids, how could I possibly explain it to the other parent? Especially since he had been showing signs of it before. If this dcg knocks over another kid tomorrow and ends up hurting them, it would be tough on you.