What does one do in potential custody battle with an alcoholic father?

I know someone that just had a 6 month old baby w/ someone that smokes pot, drinks every day & stays out all night long. He isn't legally smoking marijuana either. She is a single mom that works 5-6 days a week and does the best she can. She loves him but he is unhappy in the relationship and calls her "Crazy" for having a problem with him going out all the time. Say's SHE is the reason he leaves because of her mood swings?! She is a very sweet person that is still hormonal after having a baby in my opinion and he makes no sense. Say's he'll get full custody of their new baby by proving that she has a personality disorder. I feel he is trying to make her feel like she IS crazy because she calls me crying hysterically asking me, "Why is he being so mean to me? How could he treat me like this?!?" He get's a kick out of watching her cry and calling her names and then leaving. Does anyone have any advice for us? Has anyone ever been in this situation? Also she wants to file a restraining order against him because she is in fear that if he gets 50% custody that hi will put the baby in danger. Which he has insisted on driving w/ the baby in the car after drinking five beers. Any answers would be very helpful! Thank you in advance!