Who's better at fighting their way to the top of the greivence pyramid? It's all about the greivences theses days. It is all about who feels more oppressed no matter if the oppression is real or imagined. If you cannot accept reality the only sensible thing to do is to gripe and moan about it. The acceptance of pity is some kind of virtue nowadays.
I think the bride takes precedence. It's her wedding, a very important day for her. If she invited her blind friend then they should really appoint a chaperone to guide the blind man around, or have three different volunteers that can take turns guiding the blind person around. Maybe she could even consider holding the actual ceremony outside, and the blind person could quickly visit for the ceremony with the dog and not attend the indoor party.