If she wasn't my sister I would sever contact and move on. But she has a good relationship with my (grown up) children and sees them regularly.
I moved house a while ago and she wouldn't come round to see the house. Then she waited until I was at work and arranged to come to see my daughter and asked her to show her round.
I bought a business and several friends helped refurb the building. At the opening I invited prospective customers and the people who had helped. My sister was so angry about this she wouldn't come into my business for over 2 years, but regularly arranged to meet my daughters for lunch at the cafe two doors down.
i recently got remarried. At my wedding she sexually proposition 3 of my husbands friends and was rude to one of my friends over an old incident with my friends daughter. One of the guys she had propositioned was recounting this story to his mates, but forgot that one of my sons was there and heard that his aunt had been offering "favours". He's early 30's but was so embarrassed he got up and walked out!
I am hosting a personal celebration in the summer and want to invite close friends along. But I am so torn about what to do with my sister. If I done't invite her my kids will likely kick off. If I do, she is a loose canon. Any advice
Why don't you just tell your kids that you need some space and time away from sister, but they are free to have any kind of relationship with her as they wish?
Then go on with your life.
I agree with the above if you know she's a loose cannon then don't invite her.
If it was me and my sister, I might ( inbetween now and the summer when your personal celebration is) try to patch things up slowly? That way you're showing your family you are trying. Then if you see changes you could invite her to part of your celebration for like a couple of hours? Also being the oldest I'd set a few ground rules between you and her, if she was to come that is .