FindLaw Answers User Question of the Day: Who Wants a Puppy?

Contracts meets consumer protection today in FindLaw Answers.  Put your Greedy smarts to use to help out user donnak69, who has a problem with an item she's sold:

Our dog had a litter of pups, which we sold.  One of the buyers has decided she doesn't want the puppy after having it for a week.  We don't want the puppy back. So far, the buyer has not paid any money.  Do we have to take the puppy back? or can we refuse?

Now, obviously, anyone who would want to return an adorable puppy is a heartless, soulless robot-person.  Nevertheless, donnak69 needs to know what her obligations are after the sale.  Do her prior representations to the buyer matter?  Is it a question of state law?  Does it matter if there's a written agreement?  Ponder these things, and click on over to this question thread to help out.