its good that you have picked up on this at such an early age, it is quite normal for puupys to mouth as this is a way in which they interact with their littermates however they learn off the bothers/sisters and mother what is acceptable level of biting. as you are now the mother role its important you learn her that this biting is unappectable otherwise it will get worse as she gets older.
the first and main thing to put in place is the rule that hands are not play toys, this tends to be mostly men who playing with the dog will play fight with the hands, this sends the dog the singnal that its ok to play and bite hands.
next whenever she bites/mouths you you need to really object to it, best ways I have found that work the quickest is to just shout a really loud NO! in a stern deep voice, then straight away turn away from her and blank for a couple of minutes, repeat this exercise everytime she bites. if you dont make the 'NO!' comand loud and deep she will think your just playing. The first couple of times you do it may scare her a bit but thats what you need, its not as cruel as it sounds and works quick.
not sure what other advice you have had but if anyone tells you to tap the end of her nose then dont as the dog's nose is a very sensive part of its body and this is a uneffective and unpleasent way to correct her.