"You ask me this question every year, Enola." And his answer was always the same - it wasn't that he was being sexist, but he had principles. Nevermind how strong she was and how badly she beat him up each year - he just refused to do it.
"Ask me again when you have me broken and bleeding all over the floor. Although this time I'd prefer it if you wouldn't stomp on my balls." She had reduced him to tears last time, and it wasn't from laughter.
If she'd just adopt a male form, Ryan would have no issue with it whatsoever.