
So long as she is still growing and not a total skeleton, ie emaciated, i wouldnt panic.
She has another 6 months at least of upwards growing to do, and she really DOESTN need to be carrying any extra weight whilst she does that, that will only damage her joints and muscles.
Sorry frank, but thats rubbish, overweight is FAR FAR worse than slightly underweight, especially in a young dog who has plenty of growing left to do!
*(i do mean SLIGHTLY underweight, i do NOT mean starved!)
It is freqently tempting to push dogs to look like miniature adults at 6 mnths old, they should not do, they CANT achieve proper muscle tone and weight until around 2 years old, more in bigger breeds. Any weight you get on a 6 month old will just be fat, and no animal needs large amunts of fat to carry around. Also if you over feed you may well just make her more bouncy and hyperactive, which again wont do her any good.
Em