People who have never had to deal with a child who doesn't sleep simply don't get it. There comes a point when you would be prepared to do almost anything, just for a bit of relief.
If they resist controlled crying in that utterly desperate state, believe me, it isn't because it's difficult. It's because they believe in the very core of their being that it's the wrong thing to do for their child.
DD was a terrible sleeper, I felt as though I was being tortured. I read loads of books, tried to follow all of the advice, but it didnt work. I'd have considered paying someone to help, if I'd been persuaded that they could resolve the problem without resorting to controlled crying.
Eventually, co-sleeping proved to be the answer for us. DD is still a poor sleeper, even now, but it's much, much better than it was.
Your colleague needs support, not blame. If she has to function at work and then go home for the nightshift, she is probably right on the edge. Poor woman.:(