Everyone has given you good advice, but if it doesn't work, collect for the dolls you have and enjoy them. When you are older and out of your mom's house you can get a ton more dolls.

I only had 3 dolls when I was younger. It wasn't until 10th grade that my mom decided I could start getting more than that. She just didn't think a young girl needed to have so many expensive dolls, but that I needed to enjoy the ones I had. Now I have 11, and I think they are more special because I've collected them over most of my (relatively short) lifetime, rather than get them all at once.