Fortunately she didn't use a debit card. Ask for a "chargeback." Use that word. Don't just dispute the charge, then resolution will be under the control of the scammer. Say, "I want a chargeback." Under Visa Int'l/MC rules, the bank has to initiate the chargeback and take the money back from the holder of a merchant account who has charged your sister's credit card. Remember the magic word,"chargeback." Note also that too many chargebacks will cause the termination of a merchant's account.
