What did he end up wearing for your wedding? Personally I wouldn't dream of turning up to anyone's wedding, let alone my own, in a Dinner Jacket. Dinner Jackets are not in any way appropriate wedding attire.

Were that to have happened to me, the options would have been:
a) Turn up in whatever of my own clothes I have with me, well-fitting casuals are smarter than ill-fitting evening wear.
b) Chuck a massive tantrum and not go.

Either way, I would have instructed my ushers to keep her away from the event.

So, your options here are:
a) Take her dress to the cleaners, just to make sure it looks nice for the wedding
b) Take the bridegroom's kit back to the shop to exchange for something smarter.
c) Go to the wedding as normal, quickly get embarrassingly drunk, and throw up on her just before the photos.

If you can't get drunk quickly enough for plan (c), ensure that for any photos you are in, you are making bunny-ears on whoever you are next to.