How to deal with vindictive bitches?

I used to hang out with this girl at the start of college, she seemed cool and I didn't have anything better to do, so I fucked her a few times, I kept telling her I'm not really interested in anything other than sex.

And as soon as I noticed she is developing some feelings I broke it off, now the thing is she doesn't want to accept that it's over and keeps hanging around me, especially when I'm with other girls, she'll throw this drama and act like we are in a relationship, even going as far as saying we're together to girls I don't know.

I've told her to stop, that kind of shit disgusts me, beeing around her makes me want to break her jaw.

She acts like a 16 y/o school girl and pretends she's this little saint in front of others, so peope are inclined to believe her.

This is all very new to me, how do I apporach this situation?