She is young, she will learn. Almost all pups go through this stage.

You need to pick one method and stick with it. Consistency is key. Probably a sharp "No!" and replacing your hand with a chew toy would work if you were very - doggedly - consistent. Keep lots of "okay-to-chew" toys around, so there is always one handy.

She may be stubborn, you just have to be MORE stubborn!