If you paid $1800 for a puppy, I sure hope you got a reciept or at least some kind of record of purchase (credit/debit card slip). You might have a good chance to prove that you purchased the puppy b/c this bill would be dated BEFORE she registered it.
However, my suggestion is to call a lawyer tomorrow and explore what you can do. That's your best move for something like this. If worse comes to worse, you can take her to small claims court to get your stuff back. If you win you might also be able to make her pay your legal fees.
Best of Luck!
EDIT: I guess Brad beat me to it.
