Hi Calandra. Bailey did the same thing when he was 10 weeks old. He would growl and nip at hands and fingers while playing or holding him. He would also bite our toes and pounce on our feet like he was playing a game to catch them. I think the reason they do this is because they're still learning bite inhibition, which they would have otherwise learned with their litter mates.
Bailey will be 4 months old tomorrow and his nippiness has greatly diminished. He still gets a little mouthy and will let out playful growls when he is overly tired or needs to be taken out, but he has learned to have a very soft mouth by this point. Your little one will get there too.
What helped with Bailey when he was that small was letting out a loud, high pitched "yip" whenever his teeth made contact with skin. It worked pretty well for awhile. After a few weeks he seemed to become desensitized to that, so I started making doggy crying sounds -- you know that whine dogs make. That worked really well. He would stop immediately and start licking where he has just nipped. The other thing that worked was just stopping play. I would get up and walk away, or cross my arms and ignore for a few seconds or a minute or two.
Good luck! This is just one of those things she will have to grow out of with a little help from you guiding her in the right direction.
Cheers!