A year ago, we went with friends to Beaver Creek skiing and stayed in their 2 bd at Sheraton Mountain Vista, It was fabulous! They told us not to worry about reimbursement for room, just split rental car and groceries. We offered to pay for rental car while when we picked it up, but friend already had reservation so he said, when he gets the bill he would let us know what we owed. While on vaca, we bought nice dinner one night at Westin and never let them buy a drink at the bars all week, split groceries and paid for 1/2 car later when bill arrived. Also sent nice thank you gift. I think it was fare, I actually offered to pay entire rental but my friend said no, because he would of rented a car with or with out us there. We had the best time! There are no ill fillings after the fact, because things were spelled out and we were appreciative. Another factor was my friends sister and cousin who live in Colorado were with us all week and we bought dinner for the entire party. A little appreciation goes along way! You should, just tell your friend that your sorry you didn't lay it out more clearly before the trip but she needs to at least pay for 1/2 of the rental car, and because she is so unappreciative you should never invite her again. And again I would send the money back to the relatives. I hope you at least had fun with her, if not that is a even bigger reason to never invite the ungrateful {person} again!