I don't know what catholic school you go to but...
I've gone to catholic schools all my life and I guarantee you we all fappity shlick shlick. The only difference is if you're ashamed of it or not, which you shouldn't be. Completely natural. And satisfying :D
She probably asked because she and her friends were talking about how everyone masturbates. Me and my friends used to have that discussion a lot in religion class last year.