I (44M) and getting married to Amber (35F, fake name) next weekend. On Friday I got a call from my youngest sister Luna (34F, fake name) asking if I could pick her up from the hospital as her husband was away with work. Her job can be really physical and she’s extremely outdoorsy and active so her calling to be picked up from the hospital isn’t unusual. When I arrived to pick up Luna she was a bit of a mess covered in blood, and when she smiled she was missing a tooth at the front. Turns out she’d come off her bike and smashed her face on the pavement.
She’s knocked out a tooth, got a fracture to her wrist, grazes and cuts all over including her face, and had broken her nose with some awful looking bruising around her eyes which has now come up. Luna’s fine just annoyed she can’t ride her bike and needs to rest. She did ask me not to tell Amber which I thought was weird.
When I told Amber than Luna was hurt, she asked if any of Luna’s injuries would affect the wedding. I said Luna had a fracture to her wrist so might have to carry her flowers differently and might find having makeup applied uncomfortable as she had broken her nose.
Amber told me that I needed to tell Luna she couldn’t be a bridesmaid anymore. I disagreed as I don’t want Luna to be the only sibling excluded, especially over a broken nose. Amber said that she didn’t want wedding pictures like Luna’s, she wanted pictures she could be proud of. 
In Luna’s wedding pictures she’s got a busted lip because she got punched at work a couple days before her wedding and her husband had a cut for his forehead from headbutting a table during his bachelor party the weekend before the wedding. In those pictures you don’t see the injuries straight away, you see how happy they are. Amber then told me that she’d told Luna that if she had any injuries to her face in the run up to the wedding then Amber was going to make Luna just a guest. I told her that I wasn’t going to tell Luna that she couldn’t be in the wedding party over a broken nose.
Amber’s gone to stay at her sister’s as she’s mad at me choosing Luna over her and our wedding. Her sister has messaged me saying that Amber’s considering cancelling the wedding because I’m not onboard with her vision for our wedding and said that I’m being an asshole for not prioritising Amber and her feelings. She also said that Luna knew what the consequences of getting hurt so close to the wedding would be.
AITAH for not wanting to remove my sister from the wedding party over a broken nose?
ETA: This has gotten so many more responses than I ever thought it would. I’ve been reading the comments and it’s been mentioned a few times about Luna’s injuries and been speculated about how she gets them. My BIL is not hurting her, nor is she doing it for attention. She works in private security, she got punched before her wedding day breaking up a fight. I was there was my BIL cut his forehead, I saw him headbutt the table and went with him to the hospital. When she had her cycling accident, she was wearing her gear, had her helmet on but she hit a steep curb after swerving because someone opened their car door into the road without looking. Before this her last hospital trip and accident was just before Christmas when she broke her foot after dropping a kettlebell on it. Last year was That accident should have made me realize about Amber as she was upset that all the pictures that had Luna in them from our family Christmas Luna had a boot on her foot. According to Amber it was distracting in her pictures and there was a few comments on it on Amber’s Instagram when she posted the pictures.
I’ve messaged Amber and she’s coming around this afternoon and we are going to have a talk.