I agree that you co-worker seems to fit into all three categories you listed. I'm also childfree and I admit I do not like any children, but that doesn't mean I would rejoice at the death of someone's child, especially if it was the child of someone I knew or who I'm close to. Your co-worker probably figures you have no place to grieve for your friend because you don't know what it's like to be a mother or be pregnant. In any case, I think the response (or lack of one) you gave was the best thing you could have done - whatever you may have said, your co-worker may have interpreted it wrong or twisted it around to make you sound like some kind of spiteful witch. The childfree don't get a lot of praise, so I wouldn't put it past anyone to do something like that.