what does the GF like to do? what does she look for in a resort?
My non-diving wife loved Plaza resort at Bonaire. A nice and quiet beach, great restaurants around the island and interesting topography for driving around. But we are not into night life so that worked well also.
bonaire reefs are in great shape and lots of choices for photos.
My wife is happy sitting on the beach reading while I dive so that resort was very good for that.
We also liked Grand Cayman but I like the reefs better at Bonaire.
If you do try Grand Cayman, if you ask all the hired help you meet where they were from originally and how they got there, you get some really great stories. I loved that as much as the diving.
We also loved Osprey beach resort on Grand Turk. It does have some really nice wide angle locations within 5 min of the beach there. Its REAL quiet with a nice beach. My wife was the only one on the beach, except for when the wild horses would trot by.
After the first drink, you never have to give a room number again - They know you for the rest of the visit.
We like quiet islands and grand turk fit that nicely.
There is a nice ancient anchor grown into the coral. You need a wide angle to get the pic well. Alexander is the local grouper that comes to meet the divers. He offers some nice shots that are up close so wide angle works well also. the turtles were very cooperative for photos when we were there. there was essentially no current on most dives so setting up for photos was fairly easy.
You can get in lots of diving as the boat trips are 3-5 min. They will go out many times a day for those interested.
hope that provides some ideas - if you prefer the quiet side. If young and wild, Grand Cayman is better, most likely.