I feel you. I wanted to get certified with my husband on our honeymoon, but it turned out he had a medical condition that precluded it. Then a few years later I got certified with a good friend. Although she passed the course (half the people didn't!), she struggled and felt anxious, and never dived again. For a long time she was saying she was up for going diving sometime, and I tried ways to help her feel more comfortable, but she just never quite took the bait. I eventually let it go. I've had other friends who wanted to get certified, and I've offered advice and support, but still my only dive buddies are the ones I met diving.
I'm a little unsure what you're asking for, though. Do you want help with getting your wife certified? Or have you accepted that it's not going to happen, and are looking for ways that diving can still be a part of your life, even if it's not a part of hers?