She will probably grow to be over the standard (7 pounds), but I don't think you need to worry about her being overweight at only 12 weeks. I have a yorkie that was estimated to be around 6 lbs full grown according to the size chart that is sometimes used a rule of thumb on here, and she is now almost double that. The bottom line is you really never know 100% how big or small these little pups will be.
