during this time this sis fought dirty, told some lies and just made the whole thing worst. But we were always close and I can't imagine waiting til some awful time to work this out. If she would call it would be easier but she won't.
The first thing you need to do is realize that your sister is not who you thought she was, and she will never be who you want her to be.
You have two choices: you can either accept her as she is and go forward being civil and polite, mending the rift and making peace for the family. Or ... you can decide that you can't forgive her until she apologizes, which she never will, and go forward without her in your life and causing stress for the rest of the family.
Personally ... I read what she did and thought to myself, "Really? That's all?" I don't mean to belittle the hurt you feel or the fact that she was manipulative, but I think you need to go back and re-read your explanation. She didn't actually do anything to YOU. She didn't do what you asked her to and ignored your request, but you didn't get hurt. You're still in the same situation you were in before all of this, right? Probably a bit better off financially since you've cut your son off and aren't paying for his school or anything.
Your son is the one who got dumped on here. His aunt coerced him into a job he wasn't sure about but took anyway, and his parents cut him off so that he didn't have an obvious other choice. If you want him to walk away from the situation with your sister, then give him an incentive or help him with a plan. If he doesn't want that, then that's not really your sister's fault. Sounds like you may be blaming your sister for your son's choices, while not providing him a better option.
I'd talk to him and find out where
he's at -- he may be feeling better about it all than you think. But either way, I'd move past it and move forward. You don't have to agree with everything she's done to be civil and make peace.