My grandparents are upset at my sister

So my sister was going to get married this month and has been telling my grandparents that it was going to be on the 20th which is a Saturday, but she changed the date on them the day before Saturday. We found out by my brother who called my nana asking her where were they, which she replied home. He then said are y'all going to be coming late to the ceremony. My nana was confused by his question as was I. Turns out her wedding was literally today. He called them an hour after it had started. Both my grandparents were upset because she lied to them so they wouldn't go instead of telling them straight up that she didn't want them. I didn't even get the invite until today at 2am and she even told me that it was tomorrow. I had no idea what date, time, place, or anything. She had basically kicked me out of her wedding after she had asked me to be her maid of honor. First she had told me that I needed to lose weight and called me fat, then asked me if I wanted to be her maid of honor and I obviously said yes, she then said that I was going to be in charge of throwing all the parties. I told her that I've never been to a wedding or party so I had no idea what to do, she then "reassured" me that she would help me since I was inexperienced she then changed it and said that I didn't have to take the responsibility since I didn't have money to pay for all of the parties which wasn't true, she then posted it in the group chat that she knows that being a brides maid can be stressful and if we want to step down from the position that we can I knew that that message was intended for me. She then gave my maid of honor position to a girl she knew that I did not get along with that I used to work for. She also chose her friends over me and treats them more like actual sisters than me. She never includes me in anything not even in family trips which is her, her now husband, my brother, and his gf. She even posted things on social media saying that she "loves" me even though I don't believe her. Which she has proved the opposite with her actions.