I'd leave the two plates in... if you decide not to go, she'll probably have a few people that bring "uninvited guests" that will be able to take up your meals.

Try to go, though. I just had to "fire" one of my attendants (though that was 3 months before the wedding, and because he wasn't doing the things he needed to get done) and I'd be disappointed if he didn't come. Your situation is a little more severe... I can't imagine trying to replace someone with only a few weeks to go!, but it may damage your friendship more if you don't go to the wedding.

Stick it out, have a free meal and some free drinks, grin, and bear it.