Why would my sister do this? ?

Okay, well my sister fell in love with this one guy and they were in love forever, no joke, about 6 years, but afer high school he moved on and she still has feelings for him. She once told me that she tries to get guys to fall in love with her even when they're ugly and when she doesn't like them. I thought that was pretty CorrUpt and messed up! So I went o with my life and I was talking to her about this guy I like, I told her about a thousand times that I didn't want her to friend him on facebook. A couple of weeks late she friends him while I'm right there , sitting next to her. I feel like she has been traumatized from her past relationship and idk if she wants the guy I like to fall for her, but it seemed pretty odd. Does she have bad intentions? I don't know how to react or respond? Help! Thankss