That's just silly that she would have a problem, we didn't have children at our wedding reception....but that's children that take up a seat etc. If someone had a little baby then no prob at all, what trouble is a 4month old going to cause?!?!
I would speak to her about it, really I can't see the problem & I must say you are a being very good about it.........I wouldn't travel for it if that was the case.