I'd file a harrassment report over the friends calls/texts and have the deputy/officer tell her to cease right now. I'd tell the new owner I was sorry the horse wasn't a good fit but that you have disclosed everything and it was on her to make her own decisions. None of this is your fault. I'd also drop a line to AQHA that I had sold the horse and give them all the buyer's info, and request they take the horse out of my name, ASAP. If push came to shove, I'd pay for the transfer (actually, when I sell a horse I do the transfer for the buyer. They get a copy of the papers showing that I've signed everything over to them, and a bill of sale. Then I drop the papers in the mail and send the check to AHA, PtHA or AQHA myself. That way I know it gets done.).