You have the burden of proving your claim in court. In other words, what evidence do you have that the person actually charged the $6,000? You should have copies of the store receipts with your friend's signature. Also, what proof do you have that the $6,000 was not a gift? You should be ready to have your friend say that the charges were a gift. If you have e-mails or other documents from the person admitting the debt, it will go a long way towards satisfying your burden. With that said, because every case is different, it is impossible to tell you the likelihood of the success of your contemplated lawsuit.