I'm confused
are you leaving for the day of the wedding only or for several days?
If it's for the day, I believe she would be much better at home maybe closed off in the living/family or kitchen area so atleast she has familiar surrounds... you can always just clean up where she pottied, when we must leave the house for several hours, we leave the lights on inside and outside too and the tv with nice cartoons playing.
-I would not put a diaper on her - what if something happens and you are running late -to have that soiled and against her skin can't be healthy -what if she poopies running and that is all over her all day
If it's several days you will be gone, you have to try and find someone super duper trustworthy to babysit her
I would hate being in your position right now, can't be easy
after all they are our babies.