What exactly should I do?

Yeah im with M up there ^. If you want your mom to understand what anime is about and the type of cartoons you like to watch and read then YOU need to be responsible for explaining it to her, that is if you want her to know. If you want your mom to continue to think that you are watching cutesy little cartoons then you can do that too, but when she wants to read your book she is going to be shocked.