OMG she is so cute! As for what to do I'm really not sure. Because they aren't exactly abusing her, and some people do choose to keep their cats outside. While I would never let my cats outside, I know that some people do it. Maybe you should tell them that she comes to your house all the time and you have fallen in love with her and would really like to make her a part of your family and that they could come and visit her anytime they'd like.