It's not too late to teach your puppy- bite inhibition. It's something you need to train, just like potty training. She also needs to learn that her family decides when it's time to play - not her. Instead, I feel the need to focus on the biting part, forgive me.
When Raven was a little pup and would bite her littermates, the littermates would yelp to let the puppy know she was playing too rough, they would also quit playing with her.
She won't learn that it's a bad thing to bite humans if you don't correct the behavior, even when it's just play. Putting your mouth on a human is never ok.
Sit down with your pup, and a chew toy and engage her in play activity. The goal here is to get her to grab onto your hands, body parts, etc., at her will. I don't offer my hand to try and get the pup to bite it, that would create a mixed, confusing message/she needs to associate the biting with play/prey behavior (later, when you put your hand out to grab her in an emergency-she may just back off, because she was taught to fear the hand). Praise her when she is playing/biting the toy. The second she grabs you, give out a loud, stern - no bite!!!, fold your arms and look away from her-the play stops here (not loud enough to scare her, just loud enough to let her know you mean business). If she continues the play - get up and move away. Let a brief amount of time go by and engage her in play again, repeat the exercise and repeat it daily.
I suspect she was trying to get your son to play with her and viewed the petting as an invitation. Your son has to tell her (loud stern) NO BITE as well, but he must move away from her immediately. I don't advocate having him work with her, teaching bite inhibition, you must do it.
I had a similar experience last week at my Monday night puppy class with my own pup. We had a new pup there, but Moby was more interested in the pup's owner. He tried to engage her in play and grabbed her arm, (he was on lead, btw) she let out a small noise when he grabbed her. My puppy, thought this 'noise' was play behavior, grabbed her again. It wasn't until he heard the familiar 'NO BITE' that he understood - oh - I can't bite her, either? Everything I teach him at home has to be cross-trained to mean -it's not just me you can't do that to, it is EVERY human.
Seems like every human/dog behavior (like jumping up and puppy biting) - I have to teach him twice - once, not to do it to me and once, not to do it to others. That's ok, he gets it really fast the second time I have to teach it.
I hope this is making some sense, as I am so freakin' tired, lol!