you could either ignore the comments about the size of your puppy, or you can take it as an opportunity to educate them. being that there is no such thing as a "teacup" and it being only a made up term describing a very tiny dog , you can tell them that . As long as your new puppy is thriving and healthy, this is what matters. I agree that it is very difficult to estimate full weight and growth of a young puppy. These little guys have surprised us! Sometimes , growing much bigger then the 7lbs range. When thought of only growing to such and such.
Have fun with your new puppy. Post pictures when you have her