How To Ask My Mom About First Bra?

All my friends wear a bra. My friends asked me if I wore a bra. I said I don't. They asked me why and I said "Because I don't need one." They looked at me like I was a freak. I want to wear a bra but I don't know how to ask my mom. I don't own any bras either. I haven't wore a training bra yet either. I have been looking at so many bras though. How do I ask my mom? I am so scared!