I don't think this is a good place to find a lawyer. Unless you want some 10 year-old representing you. Be my guest.
Oh man, now is the time to put your foot down. My mother in law kept trying to change the name we picked out for our daughter. She finally said she wasn't going to call her that, and I told her, flat out, You will not see her then. Then she said, ok ok, I will call her Emmy (Emma is her name). She now calls her by her real name, and has almost her entire life. I didn't stand for it at all. Turns out her mother picked the names of her children, and she tried to do it with me, HA! The next children we had, she just suggested names, especially middle names, and she never demanded again, because she knew I wouldn't stand for it. If she took my lemonade away, I would make a weird face, get up and get mine back, and if she tried it again, I would just have to say something. Girl, don't let her walk on you, you are a woman, and not even her birth child.