How can I feel negative about my brothers new baby?

You need professional help and you need it now. Your anger is tainting everything you do. What your mother did to you has nothing to do with your soon to be niece. If your brother wants to give her his mothers name, its not any of your business. Many other people have your mothers name and they don't abuse their children, it has nothing to do with a name and everything to do with the person your mother was. She's dead. She can't hurt you any more but you are allowing her evil actions to control your life. Get help now.