How do you deal with a sibling at family get togethers, when you don't want her there to begin with?

As briefly as possible...she's the eldest of seven, our parents were both ill, she said she was too busy to help, dad died 6 mos. ago, she apologized for not helping, said she was a "bad" sister, then soon after got mad because out of 30 people to schedule, her husband was the only one that couldn't come to the family christmas celebration, so she banned it, called and yelled at me in January, I presented reality to her, she didn't like it, haven't talked to her since. Family wedding coming up...she'll be there. All of the rest of us get along fine. Feel we communicate great...she thinks we never communicate with her, EVER. Her husband and employees do everything for her. I know she might try to do the crying and please forgive me thing again or she may just never talk to me again. How would you handle it?

I think you should do what you feel is best and try not to worry. She's the problem. It's not you. If she feels guilty or is angry then it's her problem. She needs to deal with it. She's an adult and not a child. If you try to solve her problems then it's just going to burden you and not help her at all.

My mom is going through similar problems with her sisters. It's a whole big mess. They aren't speaking to her because apparently they don't know my mom at all and are blinded with jealousy.

Stay strong. It's not easy. But be rational. It's good to be empathetic towards her but don't let her take you down too.
She needs to get a grip. She sounds like a drama queen.

edit: With my mom's sisters, I wouldn't avoid them but I wouldn't go out of my way to speak with them either. I'd be polite. At a wedding then I would be respectful of the bride and groom because it is their day and not a day for family drama.

you need to act mature and make shore your problems don't interfere with the wedding that your all attending as this will be a special day for a family member. if you think she may be rude in any way don't speak to her. if she wishes to talk ask her if you can meet after the wedding that way if things get out of hand your not putting a downer on a special day.

cold politeness. No overt hostility, no encouragement to enter into conversation. Discrete avoidance (don't walk away when you see her coming, but do your best to stay in another area without being obvious). If you are obvious about avoidance or hostility, an argument will definitely ensue, and then NO ONE will be happy. Not the time or the place for that to happen.