Why payments are final
Tips go from your wallet to the performer's wallet in one blockchain transaction, through a contract that holds nothing and has no owner. There is no TugLive balance to refund from — the money is already hers.
So: double-check the amount before confirming, and if a stream ended before you tipped, the tip still went where you sent it. If you were charged for something you didn't do, your wallet was compromised — contact your wallet provider immediately.