I'd ignore her. If she did it just because she liked it and didn't think of the wedding, you'll upset her. If she did it on purpose, you're playing into her hands.
And it really won't be that big a deal on the day to anyone but you and her, so try not to let it spoil your day.
I was a bridesmaid once, where another bridesmaid was so obsessed with being the best-looking one and distinctive one there, she insisted on wearing 5" heels, despite already being 6 foot. The bride was 5'1", other bridesmaids, about 5'6". She talked about it for weeks beforehand, how pleased she was she'd found these great heels and how tall she was going to be. I thought it was out of order but the bride just said "Ok, whatever makes you happy" and rolled her eyes a few times. And on the day? All eyes were on the bride. And if anyone noticed that particular bridesmaid, they just thought she looked like a giraffe.
So don't worry, it won't spoil your day. I'm sorry the photos won't be so great, but the most important ones won't involve her anyway.
I've been a bridesmaid loads of times and even I am not bothered about the wedding pictures that include me, I just like the ones of the bride and groom.