first of all, welcome to the site... tells us a bit about yourself. where ya from? how old are ya?

convincing your mom shouldn't be a problem. we've helped many young herpers convince their parents that keeping ball pythons is a fun, safe, and easy learning experience. just give them our link bro.
i'd say the best approach would be to show her how interested in bp's you are. the more interest you show, the easier it should be.