Strange thing, sea-sickness.
I've seen people who've sailed for decades in all manner of conditions, without the slightest hint of motion sickness ever, all of a sudden become violently ill and then be miserable for days. Even for long-time ocean racers, certain type of seas with certain points of sail can bring it out, apparently.
When ocean racing, most of our crew would prophylactically patch up with Scopolamine for the duration of the race. Even though I've never been prone to motion sickness of any kind, I would usually take some low-dose non-drowsy Dramamine for at least the first couple/few days, often stopping mid-race if conditions were easy.
The trick is starting with the Scopolamine or Dramamine (or whatever) about 12 hours prior to getting on the boat. Seems to be a lot more effective than starting while already under way.
If the wife hasn't ever tried to use something like Scopolamine/Dramamine AND started it the day before getting on the boat, it might be worth a try for her. But, you know, keep a bucket handy.