This is new to me. My 19 year old DD wants to use it to pay back some money to a friend. Is it safe? She says everyone she knows uses it. I know nothing about it. I see you can hook it to your bank account, debit card, or credit card. If you hook it to your credit card, there's a 3% charge. She wants to hook it to her debit card. Makes me nervous. Any advice? Thanks!