Hmmm.. how about using peace sign charms on things? dangling from floral arrangements on the tables, hanging from her bouquet? maybe ribbon with peace signs on it? Those are the only things I can come up with off the top of my head. Do some googling, I bet you'll find somethings. Good luck!!

Does her church allow banners? I could see it on the invitations, as part of the cake design, or maybe something where you would put the pew bows.

I Googled peace signs & went to 1st 3 sites. You could make peace signs in her "colors" Does she want a "hippie" 60's look or is she against war? I wouldn't put any writing on them, wedding is not place to upset the guests. Some were very pretty. Maybe there is a category called" peace weddings" I didn't try that. Sides of cake could have peace signs in wedding colors with B/G top piece or large peace sign covering top caketop(overkill in my book-but to each his own)I think a more gentle approach rather than an "in your face" approach would be more effective! There is a hand sign also but don't know how you would use that. I think 1 pic had a heart made into peace sign, that might be just the thing!! Good Luck!