My mommy’s credit card is being charged as well as my gift card and I cannot stop it

When I buy stuff with my Apple gift card, not only does it take it out of the gift card, it takes it out of my mom’s credit card as well. There is no credit card on my Apple ID, but a few days after I purchase something, she screams at me and says: $16 FROM APPLE! I really don’t want to lose my iPad. I went to App Store > My Account > Payment Methods, but all I see is Apple Account Balance. Is there a credit card linked to my account that I can’t see. Please help me!