People growing up and changing?

My sister got engaged.... Its exciting and fun I guess but shes wanting to do things a lot with other people and she doesnt realize shes hurting people feelings when she says she doesnt want their help. And she told my grandma she didnt want our little sister in her wedding because she wouldnt stand still she will be 10 years old shes the same age as she was when she stood in our dads wedding! So I told her I didnt want to be in it if she didnt want our little sister in her wedding. She said well i havent made up my mind yet but you were It was going to be one of her good friends a couple of other friends and then me. Her sister on the end. And i had her as my maid of honor in my wedding... I said ok. Thats fine she said well we dont always get along and me and so and so get along so i asked her. I said thats fine. Im her older sister. I had told my dad i was going to go with her at tax time and buy her wedding dress. Because i was her older sister and her matron of honor and i felt kinda motherly over her. But not now... I dont want to do her hair. I dont want to plan a shower. I dont want to go. She hates our little sister so bad because she was born and she took her old room. She wants that old room back so bad! She will tell you she hates her for being born! Because she took her room. My sister has a major middle child problem. And for her to hate our sister so much that she doesnt want her in her wedding is so mind boggling to me that i cant even grasp the whole thing. I had a big come to jesus with her! I said im not going to be in your wedding period. You pick friends over family and then you exclude your own sister! She said well they asked first... i didnt have no friends ask to be in my wedding! I just can not even get over that. Now shes saying she doesnt know who shes gonna have in it. And she might have our sister... That breaks my heart. Your siblings is your siblings! final! even if i was arguing with them if they needed me for ANYTHING i would be there for them. I am beyond disappointed and heart broken that she could think like this... I told her too. she said well everyone is telling me who should and shouldnt be in my wedding and where would be a nice place and people keep telling me ideas and want to help and i dont want their help... I said they only want the best and to help you. I made my sister my maid of honor because she was my sister i didnt ask any of my friends! Honestly i didnt care My baby had died a month before my wedding. I didnt care if i got married or not. My sister didnt plan me a shower or help me pick out anything or get me a gift or anything. And i never said one word. Til now. i told her how sucky of a job she did as my MOH. And i wished now that shes acting that way towards her sisters that i had of asked someone else... But for her to break the heart of a child thats her sister! is beyond me... Shes so childish herself i guess she cant help it. its sad.