They aren't interested in the morality of her looking for a new husband while she was still married. What they are trying to determine is if your proposed marriage is just a sham to get her admitted into the US. They want to know how you met so they can determine if you just got together ad hoc to try to figure out a way to dupe the immigration authorities or whether there was a bona fide courtship here.
Don't LIE about anything. Your lies will comeback to haunt you and they are grounds to deny and BAR further applications.

