I battled this for years. It seemed like the harder I tried to do good, the more people not doing "good" (imo) were rewarded. I had a wise T ask me once what I thought fair treatment of these folks would be, and I realized that I honestly wanted good things for them. I was just invidious of their good fate. Now when this feeling takes over I think "what would I rather happen to them?" and I find myself eventually feeling happy for them. I don't think you want your "friend" to suffer the consequences of her actions really. I think you just want to be told you are right for walking away and that you are the better person.

You are right in walking away.
The "better person" is still up for grabs, unfortunately.