"Birds of a feather flock together"
She is not a puppy at the pound that you can go and rescue. She is living her life EXACTLY as she chooses. It doesn't matter if this relationship lasts, if it's not this guy, she will find another one just like the last one.........
I am concerned that you are keeping this vigil, careful what you wish for, touch the fire you will get burned every stinkin time.
All of us were involved with that " deep down she/he is a good person". Nobody intentionally gets involved with an "ax murderer" so to speak. I have said it before, she is not who you think she is. Your fantasy is not your reality.
I would like to ask you what you are doing for YOU?
It's the weekend, you should be making some plans to get out and enjoy YOUR life.