And again, lets consider life in general - how many times are we asked to do things that we are not 100% happy with but we comply anyway - whether it be in a work, family, school or social situation? This is no different. Life doesn't always revolve around you.
Nor does it revolve around your opinion of what's right. I'm pretty sure the OP wouldn't have posted if it didn't upset her. I don't hear you sympathising with her, but with the bride.

And sure you can do something you don't want to. We all do it, right? Except maybe this time she doesn't want to suck it up. I don't understand how your opinion is more valid than hers.

If she wanted to 'suck it up' I daresay she probably wouldn't have posted in the first place.

And yes I do take issue to anyone saying she should comply 'for the sake of peace' or whatever. Honestly how is that different someone telling her to 'wear a shawl' all the time, or leave the room or be discreet? After all, it's only a small thing, right? Doing something you don't want to do? To keep the peace?

Me, I'd rather tell the bride I'm sorry she feels that way and I'm not coming than tell a nursing mother to 'suck it up'.