I might try talking to her, but really, do what's best for your own mental health and family. I would get the bike and send a small gift... and perhaps suggest a casual family celebration when she gets back. I am betting she doesn't want anyone, except the people who will drink with her, to celebrate. I am another person who thinks weddings are kind of dumb to begin with, so probably not the best person to give advice here.
Of course, I have cut ties with all of my dysfunctional relatives, which includes everyone except my dad and brother.