Dont let her do the biting when she starts it say to her firmly 'NO' put her down so she knows it is not permitted, make no game of it, give her biting toys for teething, She doesnt sleep when she is with you because she is missing her Mom ,I do agree that drinking excessively is not a good idea whilst breast feeding have you spoken to your son as he may be the one to tell his wife that its not a good idea. There may be nothing else you can do except be supportive .Good Luck
Oh boy. You are in a tough spot. Of course this is crazy behavior. I mean, who takes a baby to a club for heavens sake. And that much wine is a lot and who knows if that is it. Does your son live with the mom and baby? Is he reasonable? The problem is if you criticize this mother (and maybe your son)---- they'll stop allowing you access to the baby. And it sounds like you are her only savior. I don't know where you live if there is a child service there. I just don't know what you should do. This child most likely needs rescuing but how, I don't know. This makes me very sad. The fact that she grabs you as her mother tries to take her is very telling. My cousin who works with troubled families in our state says she looks for this. (for example, if a child is hurt and runs to her vs the parent). Does anyone see the things you do to back you up? This will be tricky----- you'll have to tread very lightly or hit with a hammer to change this. Good luck, my heart breaks for kids "stuck" like this. Maybe others will have better suggestions . . .