My sister was loaned credit cards to assist in helping her pay for bills but she used the card(s) for other purposes as for her own business and gas etc. My father told her many times to stop, he couldn't keep paying for her charges yet she ignored and prayed on his kindness ignored him and continued. And to date has not helped pay for my fathers funeral costs or my mothers extra bills in the nursing home. Leaving me holding the bag and I lost my job partially due to helping my parents with estate and now I'm claiming bankruptcy cause of that.
Good Luck!
the credit card company is NOT going to go after your sister if her name was not on the credit card account. They have no legal standing to do so. Your dad gave her permission to use the card(s).