Hi Mo,
What your little pup is doing is perfectly normal behaviour, if you think about she has just left her littermates with whom she would have played games like that with, nipping ,pulling, growling.
Now you are her new family and she needs to know that these games are not to get out of hand. I would be very careful not to let your one year old play fight with her because very soon she will be a big puppy and will want to get the bettter of him.
It could lead to him getting hurt, as soon as she starts to nip or growl, stop playing ,walk away and ignore her, may be you could play a game of ball when she has calmed down, I've found puppies to be quick at learning that nipping and growling and just not allowed, as long as you are consistant! :wink:
Play fighting is a normal part of puppy development and will not have an effect on whether she is unsociable or not, but what does have an effect is how many good experiences she has in her early life, she needs to meet lots of different people of all ages and friendly dogs , all sorts of situations that she will come across during her life, this will help her to become a well adjusted friendly dog.
Lizzy Molly and Evie