What are the quarantine rules regarding bringing dogs into Mexico? I'm pretty sure you won't easily be able to bring the dog back into the US now, even though she is originally from the US (assuming the puppymill is here). There are many high end places that trick you into thinking the dogs are from good breeders. What good breeder would sell their dogs wholesale? Then the dogs will end up who knows where, with people who will do how knows what to them? A good breeder will want to try and control where their dogs (and their hard work, money and time) will eventually end up. No matter what anyone says, NO good breeder would EVER sell their pups to end up in a pet store.

The pup is likely scared bc she was taken from her mom around 4-5 weeks old, so she could be trucked from a state likely far from Florida, perhaps Missouri (puppymill capital of US) or maybe really is from AR. Many pups die during this transport. The pups must be still young and cute while in the store windows, of course who wants to pay $1000+ for an "old" dog? Start socializing your dog as soon as she's old enough to be around other dogs. Many puppymill dogs have socialization and bite inhibition issues due to being taken away from mom and littermates too early.

To bring a dog to mexico you have to go to the veterinary to have the dog checked up and he will give you a letter that says the dog is healthy and her vaccines are up to date and is fit to travel, the same thing applies when traveling from mexico to the US. I can bring my dog back to the US, I've already done it a couple of times since I bring her with me when I go on vacations to miami.
Thank you for the helpful information you have given me, I did not know high end places did that with dogs, otherwise I would have not buy a dog from them. This is the website of the store I bought my puppy from Teacup Puppies for sale at Teacup Puppies Store
I want to put it here just in case someone was looking a dog in these website just to let them know from my experience what they can expect from a puppy bought from them.
I attached a picture of my puppy from the day I bought her, her name is Bimba

Sorry, I don't believe in "high end places" that sells pets. These are businesses that are trying to make money off those who think they're selling quality cute micro puppies. They're using people like Paris Hilton to market their tiny dogs and selling them for thousands of dollars.

What they don't want you to know is how they've been inbred or bred with sick dogs or that to deliberately breed such small dogs their organs are so small that they are at a high risk of failure or that the parent dogs are mistreated and are locked up their entire lives. Puppies always look cute when they're small and puppy-esque. It doesn't mean the business is ethical. It doesn't mean the puppy is healthy.

Please don't promote and support such places...it pains me to think how many people who are unaware of puppy mills are constantly buying these cute puppies and then how many innocent dogs are mistreated in order to facilitate these greedy businesses.

Take a moment to read this article about this guy who worked for a puppy mill. It's very very saddening...

I Worked for a Puppy Mill | VICE | Canada

Please don't support or promote puppy mills.