Should I un-invite my sister to my wedding? Please read EVERYTHING before you answer, it's a tough one!?

You're right, this is a very tough situation. So as it stands now, she is un-invited? But can you trust that she actually would not show up? From your description, it sounds like she might be liable to show up regardless. She knows where it is, afterall! Obviously your family is aware of this behavior. Maybe your fiance's side doesn't know all the details, I'm not sure. But would it be possible to talk with your family and tell them your concerns if she were to show up and maybe arrange for a couple of them to "handle things" if she starts any trouble? I understand it's hard to un-invite your own sister, but also understandable that you don't want that added stress that day. Just talk to your family and see how they can help you smooth things out if it comes to that. Best of luck!