As I reply I'm looking at marks on my hand that puppy teeth created!
Patience and more patience.
My girl is almost 4 months and everything is tested with her mouth! I trained her to sit while spoon feeding her canned puppy food so that when I catch her in the act doing what I don't approve of, I give the sit command , she stops to sit then she gets lots of praise. But even just playing fetch if her little puppy teeth catch you they cut like razors!
She has time out (crate her until she's calm) when she gets crazy and when I say crazy I mean it. She seems to get a kick out attack mode and will get puppy crazy attack mode if I don't keep her in check. The key to mine is catching her before she gets to that point and making her settle down. I don't show her praise or attention until she's in the calm mode. when you go to pet her and she mouths tell her no! Get up and stop paying attention to her. Make sure she realizes that when she bites , she will not get your attention. Mine has never done it with my husband, I guess he looks to dominate. But she did it with me and still does it with anyone she thinks she can take advantage of.
Now that she's older she knows I don't like her biting and if I growl "AT" in a mean voice she immediately stops. Naturally she'll start back again if she thinks she can get away with it so I have to be consistent without fail. Also keep her at a lower level than you. don't put her on your lap , up in your face or in a high position teaching her she's your equal. Its also not a good idea to play tug of war with her because when you drop the toy she thinks she won and puts you in a lower status in her mind. Try fetch or taking a little walk sniffing out things for play time.With Dominate nature dogs it's important that they know you are top dog. You know the saying, give an inch and they'll take a mile! It's great to praise and love her but stay consistent with what you allow and don't allow her to do or she'll get mixed signals and not know what you expect.
Patience, patience, patience. It will get better with consistency so don't throw the towel in yet.