Well, while yeah she should have checked her credit card bill more recently...
Anyone else saying she shouldn't have provided her credit card details: They are actually required on XBL Gold registration for a child's a account these days and automatically saved, in order to prove that a parent / guardian has consented to the child's online activity. (I know because I had to activate my 12 year old sisters on Christmas day, I however saw the possibility of this issue coming and told her if she bought anything I'd kill her.)
Anyone else saying she shouldn't have provided her credit card details: They are actually required on XBL Gold registration for a child's a account these days and automatically saved, in order to prove that a parent / guardian has consented to the child's online activity. (I know because I had to activate my 12 year old sisters on Christmas day, I however saw the possibility of this issue coming and told her if she bought anything I'd kill her.)