When I was younger and single and some of my friends became married and pregnant, we drifted apart somewhat. Our lives and interests were different for awhile. I didn't avoid my friends, but I didn't know a thing about babies. Or being pregnant, etc... To be honest, I wasn't really all that intrigued with babies, until I had one of my own.
Of course, I attended their baby showers and went to meet the new arrival. I wasn't a cold fish about the whole thing. I just didn't "get" what the hoop-lah was all about. Until it was my turn! NOW I get it.
Maybe your friend is uncomfortable around babies. Or maybe she had a miscarriage or abortion unbeknownst to anyone else. It sounds like something is going on under the surface. Something she doesn't want to talk about. Not exactly like she is trying to be hateful. It is coming across that way, though.
She may have forgotten she asked you about being a bridesmaid. If it all feels way too awkward and you don't want to go, you could always send her a card and/or gift and then let it go. Then if she makes it a point to ask why you were not there, you could just tell her in a nice way that you felt you might be out of place, and why. "Are we still friends, or not?"