Damn what is up with buying sick dogs. When I bought my dog at a pet shop she had coccidia. I would have bought from a shelter, but I am allergic to animals and can only have hypoallergenic dogs. The really expensive one

Anyway, in my situation, the pet store paid for the vet visits and is still reimbursing me in food for the hospital visit that I had to pay for out of my pocket. They gave me the option of giving her back, but just like you I had already grown attached to her. What I would recommend is if you have a week warranty for the dog (that means that if the dog was sick when you bought it and it was still under warranty, the shop is at fault) you contact the shop and try to work out an arrangement where you can get your money back for the medicine and the vet visit. You shouldn't have to give the dog back. It is their fault the dog is sick. They are responsible for that dog while it is still under warranty