I would buy her back pronto, get a friend to call up for you.
Just for reference, never, ever, ever offer a dog on any website for free to good home, it will encourage not only impulse buyers who will buy in haste and get rid just as quick but you are leaving a dog wide open to everything from puppy farmers to people who will buy and sell a dog on as as happened here. When people get given a dog, it often has no value to them and is far easier to give it away just the same.
The only time it works is if you give to a friend or family member that way in knowing you, they are likely to put more effort in and not be deceptive.
Why don't you call up a local rescue or breed specific rescue, if you can not keep the dog ask if they have a place for her as they will at least vet properly, do home visits and take a charity payment, if they can take her, immediate buy the dog back via a friend, take the loss of the cost as a lesson learnt and then pop the dog over to the rescue centre.
Otherwise it may well be on your conscience how this dog ends up.