nik,
We have dove with most of the different dive shops. It really depends on what you want. If a bigger boat is what your looking for, go with Captain Slates. If a smaller boat is what you like, either Silent World or Ocean Divers are good. I prefer the bigger boats that time of year because they handle the bigger wave better. Plus the people at Slates are fun.
As for the Duane for a new diver, it wouldn't suggest it. It is an advanced dive. The currents can rip. But if you are determined, most shops will require a DM to go with you if they even allow an OW diver. If you want to do a wreck dive in the OW range, try the Benwood.
If this is her first time in the ocean, let her get use to the differences between saltwater and freshwater. There is so much to see in the 20 -40 ft range in Key Largo.
In the words of my wife's instructor-Don't push her, let her lead. It will better for the both of you.