I don't think you have anything to feel guilty about now. You have learned about pet stores and won't do that again, and you gave your very status conscious cousin a sweet and probably beautiful (with a good groom) little Yorkie that she loves. And she can brag about the fact that she paid $2,200 which most status conscious people like to do anyway. So I think she has the win-win situation there. Pat yourself on the back.
