I agree with doing a referral. Another question would be what time of year did they have in mind? There's weather conditions and water temperatures to consider.
Also, do you know if they get seasick on boats? If so, focus on places with calm shore diving and very mellow boat rides. I think this is a good way to start anyway - there's something to be said for dealing with setting up gear and getting back on a pitching boat after they've got a few dives in. Seasickness is something that can be solved by most people, but if it's an issue it's good to simply not have to deal with it in the beginning.
I think Bonaire is a good place. Very dive centered so someone can get really immersed in some dive culture. Easy conditions and lots of good choices of lodging and ops. Pick someplace on the water with a convenient shore dive right out front. Possible drawback, Bonaire can be expensive/bit of a pain to get to.
Curacao tends to be a bit easier and cheaper to get to than Bonaire, and might be a good option. There's just fewer dive-centered places to stay there that I'd suggest. Conditions not always as bathtub as Bonaire but usually close enough. Go West diving has a good shore dive, boats, instructors and would be a good place to get certified. The dive shop area and adjacent restaurant can be a good place to hang out with other divers. Stay at Kura Hulanda lodge or All West Apts depending on your taste in accomodations. One drawback (or not) is that it's pretty isolated without many restaurant choices nearby, but there's enough to get by. If you'd prefer something closer to town the Marriott might be a good option even though it's not really dive-centered. I have no personal experience with the dive op there but it has a pretty good reputation and a supposedly decent shore dive, and their boats have always looked uncrowded when we see them out there.
I like the Cayman recommendations above as well, though a new diver is going to miss a lot of the stuff Cayman it's famous for - unless they're diving deeper then they probably ought to be right off. Sunset House on Grand Cayman also has it's advantages, like very good odds of calm conditions and shore diving that rarely gets blown out, although it's not my preferred place. I think Compass Point would be a really good all around experience, but it will be all boat diving and the winds at that end of the island (in the winter months especially) can make for some exciting boat rides so not a good place to start if someone's not a boat person. Cayman Brac and Little Cayman I'd probably save for a future trip when they can appreciate them better.
