My sister took me out of her wedding

Hello there, ive seen post here and there with people having troubles themself with weddings and I’m feeling abit overwhelmed and need to vent out some emotions, maybe find guidances from some of you.
So im a 22 years old woman dealing with some emotions and here is the story: I got 3 sisters. 2 of them are the oldest and are my half sisters. Back in 2019 the oldest sister got separated from her boyfriend and shes been relying on me everyday. Coming to sleep over at my place, telling me about her fears and feelings. I was there for her everyday. Im a very patient and calm person so i helped her through her situation. Then one day she met this new guy, and because she hasnt officially broke up with her boyfriend at the time (they were still living together but broken up) she started coming over at my place at night and leave with the new one, then come back between 4:00 am and 6:00 am. I got anxiety since my younger age and trouble sleeping, so i waited for her every night to unlock the door (she told me she would be back at 1:00 am) because i lived alone at the time. that was hard for me, but i never mentionned it to her, because i was happy to be there for her. Shes my big sister. So time go on, and im always with her. We go restaurants, plan dates. And she tells me one day in one of those moment as we go shopping: “im gonna tell you something, but dont tell anyone yet! Me and my new boyfriend plan on getting married, and i want you to be my bridesmaid because you have been there so much for me, i promise you will be the first to be asked” and i was floating from happiness on the moment. The time has come for me to be in my sister wedding! You know, we always wonder as kids or fantasies about being into our family weddings. And it was that moment for me. So again time goes on and i remember that little promise she made. And then the day came in 2020, it was announced that hes proposed to her, i was so happy for them. And then day by day, i see cute little invites on facebook that everyone can see that shes asking a few girls to be her bridemaids and i get excited, waiting for my turn. And then the day never came. So when i saw her someday, ive bring up the subject, i asked: “did you pick all ur bridesmaids?” And she told me that yes she did. confused i remind her of the promise she made me, and then she look at me clueless: “really? I dont remember telling you that” and she say: “anyways i only take 1 sister into my wedding to make it fair”. I didnt complain, i tend to just take the hit inside and not get upset. (Bad habit of mine). So i accepted the situation with a sad heart. Days went by and i heard she took my other older sister into her wedding with her other half sister (that is not my sister. Her half sister on her mom side). She basically said that they were pure blooded sister so it was the reason to it. So then i cried, not sure how much but a good amount. Everyone thought it was a messed up move of her to do. Her other bridemaids were all people she party with and drink. (I dont drink). So one day my family bring it up to her that it was unfair of her to do, and said i was there for her when she needed someone. I told them it was okey and theres no need to bring it up, feeling scared that there could be a problem or bothering her. And then my sister cried and came at me saying shes sorry, asking me to be her bridemaid too. Surprised and shaking i said:” yes, of course! Are you sure?its your wedding and i assure you i understand” Then finally, i became one of her bridemaids. Yay! Time go on again, im going with the girls and we pick up her dress together/ because her wedding is to be in 2021. She said yes to the dress! Time go on again and little problems rise up with my two older sisters, i had nothing to do in it though. So then finally my oldest sister kicked her out of her wedding and deleted her everywhere on social media cutting contact. Then this is when things get weird. After a little while their mom got mad after my oldest sister saying if the other sister cant be in the wedding i shouldnt be too. (Which doesnt make sense as why i should be punished for my other older sister mistakes). Then my other sister says to the oldest: “if you keep her in the wedding it means you dont care for me” . So here we are today, i received a long texts message on messenger about how she need me out of the wedding because its her wedding and she decides who is in and what not. I felt it was so unfair, my stomach ached, i cried. She sent me more messages afterward about how she told her mom and sister and they were miraculously happy and friends again. I didnt answer those message out of confusion and sadness. I didnt try to confront her either about it, im someone that need a clean mind and process things first. So here we go, do i think wrong that this situation is unfair? I know its her wedding but i dont like the though of being played. I believe im a good person too and i wonder what i did wrong. Should i confront her about it? Or what should i do?

(Out of the main wedding subject: there were also little problems i noticed since she started going out with her new boyfriend, now her fiancé. Hes a very good guy, theres no doubt, but this is more about her. She started asking me less to hang out, forgetting my birthday and asking me on that day to babysit her kids because she wanna go out and party. Babysitting has been a big problem recently, she confronted me about it that i dont care about her kids because i sometimes refuse. (But she ask me every weekends and i need my free times too. And im not a teen anymore looking for pocket money and babysit, i got my own work and schedule now) again she asked me on new year to babysit, i had plans but she didnt take no as an answer. There was also negative comment regarding some positive futur plan of mine, like “oh you wont be able to” “you cant do it”. I wonder what is going on. Maybe im just starting to see her true color or maybe shes not feeling good. )