aggressive 7 wk old female choc. lab

Question
Hi,

I have 2 lab puppies. A 4 month old male black lab., Rebel and a 7 wk old female choc. lab., Sable. Both are waiting to be fixed. Both are currently attending the vet for shots and checkups. We feed them FRM Gold, for puppies. And powdered replacement milk for Sable.  We got Rebel when he was 6 wks old. His mother was sick and could not care for him. So the owner took him in the house at 2 wks. His litter mate died. He has been inside since then and mostly around humans. He is very sweet and very smart. We have had no trouble housetraining him, nor have we had any trouble with aggression. Sable on the other hand is very independent and fiesty. My daughter says she is mean and not very friendly. I met both of her parents, both are choc. labs also and they both were friendly and came right up to me, and even let me pet them. They are not related, so there was no inbreeding in Sable's case. In Rebel's, his mother, a yellow lab and his older brother, a choc. lab had somehow managed to breed. Sable was the runt of a litter of 10 and they were kept outside until she came home with me. I know she had to be fiesty or she would have gotten run over. Trouble is: Rebel loves to play with Sable,even seeks her out and when they first start to play it is ok, but the longer they play, she tends to get very agressive with Rebel. Biting him on the ears and on his dew flaps. He will whimper but will not bite her back. Usually he ends up on his back to her. If I try to even scratch her belly by laying her on her back she immediately turns over. Rebel will lay on his back as soon as he sees me. I want to know how can I help Sable? I want her to be friendly towards people and other dogs. I am afraid that If I can't get her to calm down she will get worse. Thanks for any advise you can give.

Answer
Hello, THis is really quite funny you have just discrubed what it was like with my dogs when I brought a jack russell terrier puppy home to my year old labrador retereiver...he would bite her ears/baggy skin under her neck sometiems swinging from her skin if she got up and walked away. This is indeed normal ply behavier as my boston terrier exibits the same behaviers with my labrador reteriver as my jack russell terrier did when he was younger. females are said to be more independent and it shows in my lab she likes  a few scratches and then shes off on her own for a nap or whatever. Also some puppies are bitier then others my own lab never nibbled at all when she was a puppy wheaters my friends lab/golden Cross used to bite hands rather hard as a puppy and my jack russell terrier nibbled hard as a puppy and nipped socks as well wheaters my boston terrier never touched a finger in her life unless of course it was to lick it! I think given time she will grow out of her stage and be a well loved affectionate family pet but right now she just wants to play and thats all. I get alot of emails with peopel saying the same thing after introducing a new pup into a home that already has an older dog....they will play rough I know this for a fact as my dogs do play rough every single day...its very normal and nothing to worry about..my lab would even whine and get up and walk away from the other dogs when they were pups and playing with her....because she knew she wasnt allowed to nip hard like they were back.