let me just say that even if you get negative feedback; they mean well.
everything you need to know about your "teacup" has been stated, but 5 pounds is a tad bit on the larger side for a so called teacup. My sophie is 5 pounds (granted she is still growing). But even if you are disappointed that your baby isn't going to be small -- don't be. you'll fall in love nonetheless, and won't have the worry of your darling hurting herself, or your other dogs hurting her.
welcome to YT, you'll be addicted before long!