Pet sale fiasco

[Yazming13]

What is the name of your state (only U.S. law)? WA
My dog had puppies and when it can time to sale the puppies I admit I was very under-educated on how to proceed with selling them. I decided on a price, posted an ad on the internet and did some phone screening for new families for the 3 pups. All sales have gone well except one. I had decided to take payments. One initially with the sale and 1 payment each month until completed. After about 2 1/2 weeks, this family sent me e-mails saying the puppy had broken its leg and because of the medical bills she wants me to cut the price down by 150.00 dollars. When I said that I was not willing to do this she said then maybe I should take the puppy back and give her a refund and that I could deal with the medical bills because she could not. The next day I called to speak to her and a gentelman answered the phone. I said I wanted to leave a message for the lady who was buying my puppy and he said that he was her father. I then found out the girl was only 17 years old. I told hime what she said and to make a long story short he said that her and her boyfriend were obviously trying to pull a fast one on me and that he would take care of it. So basically she said that she was laid off and that the puppy had broke its leg which was all a bunch of lies. After this whole situation the father ask me to give her one last chance before taking the puppy back to have her live up to her end of the deal. Since that point, it has been nothing but hell dealing with her, I believe that she is mad that she got caught. I need to find out what my rights are on getting the puppy back. I did not make up a contract, but I did do a lot of e-mails and have everything that she lied about on paper. Please help me, I need to know what to do. I know I need to get this puppy out of this situation.