I'm not going to invite my future sister in law to our wedding
Why would you not want to invite her?
I just need to have the wedding in my own way.
It makes sense to want your wedding your way, but this is a family member and typically society dictates that family is at your wedding. How would you feel if you weren't invited to her wedding?
I'm just going to focus on this wedding and my own happiness. That is the way to impose my will on people.
Your happiness at your wedding is important, but so is the happiness of your sister-in-law and if you don't invite her you will cause her pain. You can find your happiness and include others at the same time, so give it a try.