If the original agreement was that she surrender the goat at a specific time and place, she would have to honor her agreement. But as you mention, she could then have attended the auction and bid for the purchase of the goat. Yes I think you are correct that telling others why she wanted the goat would probably have resulted in folks refusing to bid for it and her bid would have won the day. This is so obvious an answer that I assume there are many more extenuating details not mentioned in the story as to why the simplest, most humane outcome didn’t prevail....
It is strange! The winning bidder gave up his rights to the goat. Why didn’t he give the goat to the girl.
Must be more to the story.