Possible Abusive Relationship?

Okay so first of all this isn't about me, it's about my friend. Well, last spring (May of 2016) i was talking to my friend on our way home from our softball game. Now there were more people around so i think that's why she didn't open up as much as she could have. She was telling me about this guy she had been on and off with for about a year. She is a junior in high school and he's a freshman in college. They've known each other for awhile and they started saying about 2ish years ago. I asked her what she saw in him because she was complaining about him a few days earlier. She said she loved him. Now this was in the same week she told me he was the one this summer who had said the worst things to her she had ever heard. Now she didn't elaborate on these things but she seemed very upset about it. A few days earlier she told me about all the times he would get jealous or possessive of her. They would fight all the time and he wouldn't let her hang out with other people. She's "best friends" with his younger sister who is in her grade. She will always tell her mom she's going over to his house to hang out with his sister because her mom doesn't like him. At this point in time i can't remember tho full story she had told me on the bus, but i vividly remember her telling me with the saddest look in her eyes of the way he used to talk to her. I've told her so many times she deserves better and to just dump him. He would talk to other girls and flaunt them around her to make her jealous and it worked. Now i find out today they are dating again and he picks her up from school almost everyday. I have a strange feeling this relationship is very toxic. it may not be physically abusive-yet- but i have a strong feeling it's either emotionally (he makes her feel like the arguments are her fault) or verbally abusive. Also to note, he smokes weed and does a few other drugs and gets drunk all the time. I'm not sure what to do because i've already told her how i feel and she doesn't listen. Any thoughts from experience or advice?