Ive financed auto loan for sister and want out?

one year ago i financed a truck for my sister and every month i have a hard time getting that payments .i dont talk to her no more because we got into a big argument for the same reason. now we communicate with my mother. she gives me a check everymonth i cash it and i deposit the money in my account in case the check bounces.well this month she gave me a check and the bank told me they couldnt cash the check for me because there is no funds available.i know it was stupid of me to do ..to lend my credit card..yes i learned my lesson..the payment is 5 days late..what can i do..i am frustrated i do not want to ruin my credit..shes my older sister by the way i am 8 years younger and more responsible....seriously what advice do you give me?
i meant my credit out not my credit card