I'm so sorry that your sister put you through this. I don't even think that you have any legal recourse, most states only give you 7 years. If she wrote the iou less than 7 years ago you may be able to re-coup the money. As for the personal relationship, it doesn't sound like a healthy person to have in your life to begin with. But it still hurts that your own sister would do this to you. Again so sorry that she turned out to be a jerk!