I agree and I thought it was lame of her - it isn't like I would seat her any where near her mom knowing how she felt. But honestly I personally don't dwell on this myself. Everyone has to make their own determininations on what they feel is right/wrong or just plain old weird.
My good friend said she wouldn't attend my wedding because she just came off a big breakup and couldn't feel good about going to a wedding. To me that's odd - I mean wouldn't you want to support your friend even if it is hard for you? But that's me and I never got angry or upset at her. I mean it is your personal decision so be it. My uncle wouldn't go because every year he goes on this trip that particular weekend. It bothered my mom (her words you go away every year, but your niece only gets married once) - but I could care less.
I've heard of people not attending weddings because children aren't invited - they get offended their precious little monster can't go. I've heard just so many different things for the oddest reasons. Just found it interesting.
I typically don't take so much personally - just find that some things are interesting and seem odd to me where you take a stand and why.