Was the deal done on paper, or only by verbal communication. I am not versed in equine law, but is there a way where you could legally send her a letter stating that she needs to come pick up the horse by a certain date, and that if she doesn't then you are going to retain ownership, as it would be considered abandonment, and then you'll sell the horse for the "back board" the lady owes you for leaving her horse there. I know that boarding facilities have their own insurance anyways, but that is what they do if an owner just leaves and doesn't pay board ect. I would make sure that you do something legally to inform the owner that she needs to come pick the mare up, and if she does not, that other actions are going to be taken, so that way, she can't come back in a year and say that you stole her horse or something. What I don't get though is why she didn't come pick up her mare when she dropped your baby off. I am sure that there are others on here who know a lot more about equine law then I do, and hopefully they can offer you some better advice, but that's just my two cents. Hopefully you can work it out quickly.