My german shepherd was 13 pounds at 7 weeks, but he is a boy, so your dog may be a little underweight. Check her lineage and maybe smallness runs in her family. She will probably be around 60 or 70 pounds as an adult
It depends on her lineage, but I would say she is underweight. Puppies need a layer of fat, not a lot of it, but a small layer as they develop. At 10 wks she should have been wormed 5 times by now. A prudent worming schedule starts at 2 wks old and goes every 2 wks until 4 mo. Old, then monthly. Worms can be very debilitating, not only do they take nutrients but they defecate and reproduce inside the puppy. A puppy should be "roly-poly" til about 4-5 mo., with a shiny coat. Worm your puppy and keep it worm free, feed a nutritional diet, natural is best, but there are good commercial foods. Add Brewers yeast (inexpensive at walmart)to the diet and the coat will be AWESOME, and it keeps fleas off naturally.
To know if she is actually under weight we would need to see her. :-) Does she seem underweight to you or just a little smaller than you expect? Can you feel all ribs, see more than the first two, spine, hip bones, and not much muscle? Does she seem like a normal healthy pup or is there anything else your noticing? Did you do your new puppy check up yet (also often contained as a part of the contract and just something that always be done)? Did the vet think she seemed a little underweight then? It is a little smaller than average (which is a big gap) but could be normal for her. It could be something like parasites or could be something like liver or EPI or something if she really is underweight and smaller. Could also be she is a healthy weight for her individual self and isn't underweight at all. If something else is worrying you or you are seeing any signs of actual illness go sooner but you have a vet visit coming up for shots, deworming and check up usually around twelve weeks depending on schedule so could talk to them then if things don't seem too serious. Good Luck. Hope she is okay.