How do i secretly buy a binder?

I just got my first card ever but its basically just a card under my mothers name and everything is hers i just have the number to it, so if i was to buy something off amazon she would get the notification then ask what i bought and i havent came out to her, i dont think shed hate me or anything im just really scared because what if she DOES? then what. So im in a bit of a predicament and so lost. I wish everything was much easier. If you know anything about cards pls help.