My vote is to take her back... My experience with a petstore puppy was that she didn't live as long as she should have due to a heart condition. It's much easier give back a puppy after having her a few days than to walk out of your vet's office 6 years later, leaving your little one to be put to sleep.
No one should support that pet store anyway! Think of the conditions she must have been raised in. And the poor parents of that puppy, think of how they must be cared for.
Also to the person who says shouldn't have a dog because you can't afford it: if everyone waited to have things until they could afford every aspect and suprise that may come with it, only wealthy people would have children and pets. It's quite unfair and snobby to say that. Animals bring a great deal of happiness into a person's life and people benefit greatly from their companionship. I'm sure you wouldn't deny a puppy to my grandmother who's on a tight budget. Since her husband passed away and finds most of her hours very lonely with no one to take care of anymore.
A couple just starting out with their lives can learn a great deal of responsibility with a little dog as well. Nothing prepares you more for a baby than a little puppy.
