My friend is interested in a guy who is way wrong for her. what to do?

she is such a lovely girl. but she seems to have fallen for this MINGER. he smokes, does drugs, gets recked every night and has a rep for being from the roughest family in our town. ive tried to talk her out of it but she is so totally gagging for him :/. they were together about 3 months. well, i say together.. but they did all the stuff you do (, BJ's..), but they wernt officially boyfriend and girlfriend so he was totally using her. now, he has ended things with Beth(my friend). and is "in a relationship" with this slag Carla. he was never "in a relationship" with Beth. she cant get over him. how do i convince her he was a bad catch and she can and needs to get over him? and how do i get her out of the bad habits he got her into ? (smoking,getting drunk etc). he also got her a bad rep. HOW IS SHE SO BLIND TO ALL THE CRAP HE HAS CAUSED?!