Ah, this can be negotiated.
Years ago, a married diver posted his liking for Curacao; it offers shore diving, nice beaches that often have some onsite amenities, and it's larger and has more topside diversions than Bonaire. He could grab some diving while she hung out on the beach, then they could spend time together. I did some boat diving on a trip there.
Curacao Trip Research Notes
Curacao Trip Report with SB Surge Jan. 2019
Another option is to hit a dive destination with accommodations very close to the diving so you can get a couple of morning trips in and be back in time for lunch and to spend the rest of the day with her, and enough going on topside to entertain her. The southern all-inclusive resorts at Cozumel may have one that'd fill the bill. I hit Cozumel, but I stayed at a resort in town and did a lot of diving on a solo trip.
Tres Pelicanos & Casa Mexicana, Cozumel Sept. 2018 Report -
Tres Pelicanos/Casa Mexican Trip Report Sept. 2018
My Research Notes from Planning Cozumel Trip -
My Research Notes from Planning Cozumel Trip
An all-inclusive with a sandy beach, maybe take a day to hit Chankanaab Park and do a manatee interaction, spend time enjoying shopping and dining in San Miguel, etc...