All right, I'll say a few things:
If a woman can drive a car at 65 miles an hour on hard pavement on a crowded freeway, she can certainly drive a sailboat at 15 mph on a relatively soft surface like water.
Both people on the boat should know how to sail and how to do all the jobs on the boat, including helming.
Who does which job at any given time is a matter of what works best for weight distribution and what needs the most strength, depending upon weather conditions and who is best at handling specific situations.
It is easier for a woman to be on the helm in long-distance races where you are on the same tack for long periods of time and there are not other boats in close proximity. Let the weaker person steer and the stronger person handle the sheets and downhaul.
Buoys racing is another matter. Most (not all) women are not as aggressive as men, and they don't like situations where there are a lot of boats in close proximity. So what you do in this case is the man does the start. After the boats spread out a little after the start, you change positions and put the woman on the helm. In heavy air the man will be better positioned to handle the mainsheet and downhaul. In light air, strength is not needed, but his weight will be better positioned forward.
If there is a windy, fast-reaching leg after the weather mark, you should change places again, prior to getting to the weather mark, so the heavier person is at the back of the boat.
On the downwind legs, job or position should be based upon best weight distribution for the conditions and where strength is most needed.
Mark roundings, again, are intimidating for some people, both men and women, so if you see a crowded leeward mark rounding coming up, you switch places if necessary to put the more aggressive or experienced sailor on the helm.
This switching of places on the boat during the race is the same thing you can do when you are training children or novice racers of either gender.
You start out doing this team-switch thing in light-air conditions and gradually work up to moderate winds. And while you are doing this training process, don't ever yell and do not ever make it feel stressful to the person in training. Once she is on the helm, she is the one who is going to get motivated to figure out how to beat those other boats. She is going to start asking questions.
But the really really best way to get a woman hooked on helming is to get her racing a singlehander in a group of other women sailors on boats like Sunfish or Waves.