How can I get her to leave him and be with me?

Totally agree with redrover - she may need a reason to leave him - and that reason could well be you! She won't leave him unless she knows you're there and want it too. Try and let her know you have feelings for her without being too overbearing.

Wow this sounds so familiar to me! I was that girl (well at one time). In my opinion it's all up to her and if she wants to leave him. I used to tell people the same thing about my ex, that I knew he was a waste of time, and that there was no future there. He actually cheated on me 3 times. But eventually I started falling out of love with him. And the guy who had been trying to impress me actually is living and dating me now. All I can suggest doing, is not to talk bad about her man to her, she'll think you're probably insecure and that's it's low of you to poke fun. Also try to be there for her, to talk, and hang out once in awhile. Try to keep in touch I guess, and if she likes you now just keep being yourself.

Just keep being that adorable you and she will see it. If she talks to you about him be sympathetic to her situation. You might try asking her out anyway and see what she says. You may be just the excuse she needs to dump the loser. What's the worst she can say, No? Big deal. You can still be friends and hope that she will wake up and smell the coffee at a later date.

Stay awesome and hope she likes you. It's her choice dude. Think of it this way: if some girl did anything directly manipulative to you, wouldn't you feel backstabbed? Would you even want to go out with her? Girls say sh*t to me all the time to try to make themselves seem better than the others, but why would I want a girl who is so sure she can decide what's best for me that she'll pull some BS to do it? Answer is obvious man, just don't go down that road.