Bridesmaids??

Originally I wasn't doing bridesmaids,unless it was my grown children. then my husband got his best friend as best man so I chose a maid of honor. Here's where my headache n Drama comes in. My SIL.. ( because she's headache n drama) My Orginal date was this Sept 13th.. shortly after I announced n started planning She announced her n my Brother, 3 months before mine. We decided hubby n I to postpone.. 2 weddings and 50th anniversary was too much. Not to mention she refused to help do anything for her day. She had me as a bridesmaid, n her daughter, and another horrible woman. But all the work fell on me, my mom, dad and my significant other. Oh n my brother as much as he could working 12 hour days 6 days a week. Now I'm hearing she will be upset if I don't ask her to be a bridesmaid, and it's best if I do to save on family issues. I know exactly what she'll do.. We went through this for hers cause i called her out about not helping n she made EVERYONE miserable for it. But noone would let me step down from bridesmaid. Id have still helped, and been there, my mom has rheumatoid arthritis n cant do alot of anything, my dad tried but he couldn't do it all either. How my family works.. don't rock the boat.. and why I'm the black sheep, cause I'll capsize it.. with a smile n say Ya earned it!! However she will make my brothers life hell if she don't get what she wants n he comes anyway, which he will. I really could careless if she shows. I do care about my brother. I've waited my whole life to get married and I'm only doing this once!! I'm 46 n been with my partner 18 years.. n we just now decided we were going to do this. We have
already been through cancer treatments once, n its back so he's decided he's not going through that again. 😔 There's not much time left...😪 Don't get me wrong we've lived the ups the downs, the good the bad.. its like we are married already, I've always been okay with that, I'm still not certain I'll make it up the aisle..I personally think it's not committing ive been committed, but the no way out, solidifying. I don't exactly believe in divorce. But why do I have to do what she wants.. I was going to invite her.. just not have her as a bridesmaid. Honestly I'd prefer she took a long walk off a short pier. She'll turn my day into the s#$t show she tried to make hers to be.. that We as a family wouldn't allow to happen. She had her make-up girls do my make up horribly, talked a mountain of crap while I was running like a chicken with my head cut off making the day happen, so much so her photographer showed some compassion, but it was understood I did it all for MY family. She even didn't have me n my husband up there for grooms family photos, n cut me out of most pictures. What was my part you'll ask.. I asked her why she wasn't coming out and helping get the back yard together. It was in my parents back yard. Her response was "I wanted a venue, your brother wanted it here so i dont have to help" So I asked her what marriage actually meant to her, is it just a princess party, or do the vows, promises actually mean something to her? Honestly I do not want the drama!! I've written a poem for the entry table that basically says ..leave your drama at the door or we'll show you the door. Its much more eloquently put though. I'm once again stuck between my principles and my families, what do I do??