SO this girl keeps on talking crap about me? 10 points?

This girl I liked Lead me on and said "she didnt know she was leading me she said." She was lying and talked crap about me to my friend just to hurt me. I got a little mad and started talking to her why she did. Then next thing you know he brought her ex in and he started talking crap too, two on one. She continued to "try" to lead me on by grabbing my hand and cuddling with me. Until I realized she wants attention and would only use me as her back up when doest have a Boyfriend, it hurts of course. But after all of it I still agreed to be her friend. But now Im thinking I made the wrong choice. What some things to tell her as a goodbye that will get kind of upset or desperate to make her fell what I did, but in a nice or casual way?