Your mom is deliberately needling you. She probably likes hearing that she upset you. Don't give her the satisfaction. You have a right to decide how you will be called. Your mother doesn't respect that, and she doesn't respect you. Even when your name is legally changed, she'll probably find some other way to be obnoxious. It's sad. I'm sure you don't need this on top of the pain of a failed marriage and the strain of divorce.