I do. Don't think that I don't care. I'm your mother and of course I think it's terrible what she says to you, but I'm not blind enough to not notice that you're not exactly innocent yourself.
Sometimes you just have to be the bigger person. She will continue to talk to you like that for as long as you speak that way to her. This is really up to you. I'm sure you don't want me to talk to her mother. Or her. Wouldn't that be embarrassing. Everyone deserves respect, whether you think so or not.