I've been watching this thread and have followed it since the first post but I had nothing clever or witty or even comforting to add, and in fact still don't. But I do just need to say at this conjecture...
O.
M.
G.
You're cornered because its the 'happiest' day of her life yadda yadda so you can't appear to be nasty and 'just' sore that you didn't have an invitation (is what she'll say). (That's my take anyway)
Forget the silliness now, the poems etc (although I appreciate how it has lightened up the gravity of the situ and made you laugh).
Have you still got the save the date card? Just reply and say 'sorry I'm busy, I'm seeing a friend that day'. Dignity all the way.
That is putting it very mildly for me 