Should I tell my girlfriends mom?

i caught my gf talking to her ex bf and his friends on facebook this past week. Her ex cheated on her and only dated a month and his friends are huge dirtballs and do drugs and party all the time (typical hs jocks) shes not that kind of girl but she delt with it because "hes hot". We have been together 3 years now and last week she was talking to them like planning to hang out. I confronted her and she said she wasnt interested in him they are just funny and fun to hang out with. I broke up with her and she begged for me back for a day so i talked to her and told her she cant talk to them anymore or ever and she said she promised but needed space so i stoped texting her and (shes logged on to fb on my phone) now shes messaging his friend trying to get him to call her ex so they can hang out tonight... idk what to do, I dont want to say **** you and lose her forever.. should i talk to her mom and tell her whats going on so she stops her from hanging out with them>? (her mom wont let her hanging around kids that drink all the time and do drugs)