consumer's rights under IN state law regarding purchase of sick dog from puppy mill, Parvo

Dog buyers rights: Do I have legal recourse in Indiana for buying a dog from a :"puppy mill" sick with Parvo. To date $571.00 vet bills to save pup. "breeder" selling hundreds of dogs on-line. Address unknown. Offers to meet buyers. When informed of sick dog, offered to refund $200.00 paid. Now threatening me with $6500.00 lawsuit for slander for saying dog had Parvo & stated has many lawsuits against buyers claiming to have bought sick pups. Address unknown. Plan on having friend feign interest in an ad, get lic. plate# & have traced to get address. - Is this your question? Add additional information