I would think it to be very rude if they sold it right after you gave it to them. But if it's been a while and your baby has outgrown it or not using it any longer, then I don't see why you couldn't sell it
I can understand the giving it away though since you got it as a gift
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~Magnifique Yorkies~
Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs.
Educate yourself and buy from reputable breeders or rescue.