[JoeyP]

Sounds like you are. Dealing with two separate issues here
The nipping is one thing but it also sounds like there are some true aggression issues here as well
The nipping you stop by saying No .... Hands up and she is left alone immediately
The holding down thing isn't good for those reason.... Aggression begets aggression
You need to work with her on allowing you to take anything from her mouth at anytime
I tell all people with new pups to sit and pet their dogs .... Put your fingers in their mouths and open their mouths
This gets them to trust you and used to them having you do this at anti me
Also work with her on toys being given and taken away
Give hear toy
Andtake it from her...... If she growls ?
Immediately it is taken from her and she's given a strong NO
Soon she'll get the message