Thanks for all the responses guys.
I should just take the high road and leave it alone.
I think part of me wanted to WARN her...cause she's been with him for four years hoping for a ring and it hasn't happened. She's a nice girl and attractive, too. But her life is her life.
As for the "cruel and vindictive" part.
I just noticed a switch in his behavior when I stopped sweatin him.
It's like he no longer has control over me and he resents it.
He has cheated me out of money with regards to our living situation.
He told one of my best friends (a girl) that I'm not a good person and that she should watch out.
He texts my friends behind my back when I'm out of town asking to hang out with them (this isn't cruel but just weird to me)
He has threatened me, saying he would basically kick me out of the apartment
Also he does weird shit like wears my clothes when I'm gone and then puts them back in my closet so I won't know. (I saw him wearing my shirt once on Facebook)
I had no problem letting him borrow my clothes...but ask first

anyways...ugh...yeah roommate shit. One more month left. Thanks guys.