Dealing with resignation offers

The 2011 Dubbo Open ran pretty smoothly, with only a couple of minor arbiting issues to deal with. But I did come across something I've never personally witnessed before (although I have heard reports of it happening elsewhere).

On the lower boards there was game where one side was easily winning. The player was 2 queens ahead and was a few moves away from mate. She clearly new what she was doing but at one point ,after moving, she simply asked he opponent "Would you like to resign?" in the same manner you would offer a draw. The opponent said "No" and the game soon reached its conclusion.

It was a minor breach of the rules ("disturbing your opponent") and I did not interfere. But if such an 'offer' was allowed in the rules, I wonder how you would signify it on your scores sheet?