I don't have the cultural issues that you do at the moment with my current
GF, but have been "there" so I know how difficult that can be.
However, my solution to indoctrinating her to sailing was to give her enough confidence to fall in love with it on her own. This was a person that not only was terrified of seasickness but also didnt know how to even swim.
So instead of heading off to get my US Sailing Certs alone, I brought her with. It was a difficult battle getting her to do that part, but once she passed her exams, suddenly the beast had been unleashed. A few months later she was at the helm
in the BVI with a smile on her face.
My instructor who cruises with his wife told me that his wife gives private lessons with many women that are "Tired of just making coffee" on the boat. Some have been doing only that for years while others want to break free from the dependancy of looking at their partner for anything technical or dangerous without understanding what is actually going on.
Perhaps giving her the knowledge (Power) to understand sailing instead of just depending on you in that regard would do the trick without any convincing needed. If anything, it would really spell out if it is a lifestyle that is compatible at all in your relationship.
Best of luck to you and I hope that you can somehow find a way to demonstrate to her that sailing opens up the doors to experience some pretty incredible things that do not even involve the act of sailing at all. (Sitting on a deserted beach, just the two of us, sealed the deal for me.)