Shorter than a week.

[Damselfish]

seeing as you didn't specify cheap, or Caribbean...

Spirit of Freedom - Coral Sea and Great Barrier Reef Dives Cairns

Cairns Liveaboard Scuba Diving Adventures with Deep Sea Divers Den.

Mike Ball Expeditions | Cairns australia

Four Seasons Explorer

If the main issue is that she will be bored on a boat for a week, you might look into some of the liveaboards that are a week long but have a reputation for having more non-dive activities. The Cuan Law (BVI) is often mentioned for this. The Aquacat in the Bahamas might also work.

If she just doesn't want to be on a boat for that long, there's some really luxurious liveaboards in Indonesia that might change her mind. And they'll make the others look cheap.

 

[diversteve]

There's the upstairs cabins on the Turks & Caicos Explorer. You mostly stay on the boat and dive though as there's no civilization near where they moor. It's a very dive focused trip. Might be boring for a non-diver.
The better cabins on Nautilus Explorer are similar. The only problem is the only non-dive intensive itinerary is the Sea of Cortez and they don't seem to be doing it 2014/15.
Most of the Aggressor's are bunks. Nice bunks on some of them (personal flat screns) but still bunks in ensuite cabins. Dining options seem to be nicer across the Aggressor fleet.
Cuan Law is a good option for non-diving activities. It's a huge boat due to the design, the lounge must be 30' or more across. And they do a lot of non-dive things all through the BVI's since they're never far from a small island or port. We saw someone waterskiing from it.
Arenui makes the rest of them look plain by comparison. I've read Domai is even nicer. I don't know about non-dive activities on either. I think they're mostly sold out this year.
There's also the Paul Gauguin South Pacific cruises. They offer both daily diving and other excursions at ports they call at. It's a really a small cruise ship.

All of these are a week/10 days plus flight time.

 

[kenny kustom]

She dives.
It just a compromise.
She'll do a lob, as long as certain criteria are met.

If momma ain't happy......

 

[ppatin]

No personal experience with them, but Juliet does 5 day trips to the Bahamas occasionally. Looks like they won't be doing any until late this year.

Liveaboard Diving Vacations - Juliet Sailing and Diving

My first liveaboard trip was one of their five day trips to Bimini. I wasn't sure I'd enjoy a liveaboard so I preferred not to commit too much time & money to my first one. As I've said many times before on this board I had a great time, my only regret was that the trip was so short.

Also OP, there are full size beds in the Juliet's cabins and a pretty decent amount of privacy