My son is back with the girl I don't like?

I have a son that is 17 and will be 18 in a few days. He was seeing this girl a few weeks ago and I didn't get a good first impression from her. I tried to like her and tried to be social but, she hung on my son every second they were together. She would come over after he would drive to get her because she got her license taken away.(first red flag) then, she would come in the house and go straight to his bedroom which we said that they had to stay upstairs in the family room not the bedroom. She wouldn't say hello or anything. She would leave and the same thing. After two weeks of him blowing $700 on her because she wanted to go out to dinner instead of eating here and the movies and so much more she breaks up with him and said she was with many different guys. She is 18 years old and has been engaged, slept with 6 different guys and contracted a VD. My son wants to date her again and is going back to the same ole ways of her being with him 24/7. He is blowing off all of his responsibilities and work to be with her. He already said that he will be 18 soon and I cannot tell him who to date. He is right but, there has to be something that I can do to stop them from seeing so much of one another or all together. I seriously cannot stand her and the way she comes over with her a$$ sticking out of her shorts all the time is disrespectful as well. I need some help here please . I know that if I tell him to stop it will push them closer together. I need some advice. Thank you for you help.