Going to stray against the grain a little bit here. NTA

There is no harm in asking, all you did was invite her and have a proposal. Just because she doesn't want to RAISE a child of her own doesn't mean she would be 100% against the idea. I think the fact that she exploded on you guys makes her TA. If you tried to pressure her by blackmail or something, that would make you TA.

Most of the arguments here is "you knew she hates kids. You asked her. You're an asshole." but I personally can't find any structure in the argument when you put her in no harm. It's a huge thing to ask, I understand, but we need to understand that you fully would have accepted 'no' as an answer, disappointed, but I assume you would be mature enough to not literally throw a tantrum over it.

Bottom line: Sarah is over reacting. As is everyone in this thread. Find someone else who is willing to do so, and good luck. I'm sure you both will make good parents.