My elfin boyfriend is attending my sister’s wedding?

So I’m 24 and my sister (17) is getting married to her fiancé. She really wants me to come as she thinks it’ll be a special time for us to bond. The problem is she’s attending to a whole elfin wedding since her fiancé is a high elf, and elfin weddings are very different from human ones. She asked if I’m still going to come if she’s going to have it as an elfin wedding and I said yes. So the ceremony will be held outdoors in the forest and all the guests will have to be completely naked. No jewelry, no makeup, no hair styling, nothing. I can’t bring myself to do that, I’m really the modest type and the thought of it makes me very uncomfortable. I’m not sure what to do and none of my friends have experienced anything like this. I really don’t want to miss it but I don’t think I have it in me to actually do it. My boyfriend is very adamant that I should just go through with it, he’s 1/4 high elf and he’s been to elfin weddings before, so he knows what it’s like. He said it’s really fun and that it would mean a lot to my sister and her fiancé, and they’ve already told her that they’re okay with it. It would be a big blow if I didn’t come because I’m her only sister and she said that it would mean a lot if I could come because she remembers how I always used to play elf with her as a little girl. I really can’t decide and I’m very conflicted. Advice?<br>tl;dr: my sister is getting married in an elfin wedding and I have to be naked there