Your little girl somewhere along the way got the idea that its fun to run up on Mommy and bite her on the nose
It might be that she never learned the social interaction from her mom when she was a pup or that she gets attention somehow good or bad when she does it
you need to take away the attention
best id to catch her before she nips ... if she is running up on you
Body block her
and it's NO!
and that's it ... no talking to her
no scolding
no laughing
Puppies live for our attention
and it's better to them to get bad attention than no attention at all