I've been on two diving cruises. We had 3 divers in an interior stateroom on a Carnival ship last week. It was the Ecstasy out of Galveston. (Carnival's staterooms are about 50% larger than NCL). There are lots of pegs, racks, hangers, etc. in the room. You will figure out a way to hang RINSED gear. If you don't rinse it well, your room will get funky. Don't take a shower with your swimsuit or wetsuit on, however, in order to rinse them. If there are sea lice in your attire, you will activate it's venom while scrubbing. Wash them separately from your body.
We also bought a wetsuit dryer on Ebay, it was very useful and we managed to use it in our NCL stateroom when it was just my husband and myself. We didn't try to fit it in with our daughter in the room on the Carnival ship, however. A handy option for us on this last trip was that the first day we dove in Cozumel. The next day we rode the ferry back to Coz from Playa del Carmen. The dive op (Aqua Safari) kept our gear overnight, so we didn't have any gear to lug back and forth (or store in our staterooms)until the last dive. I did keep my reg with me, however. (I'm passionate about my reg, lol.)
I reiterate the statements by others regarding the sanitary issues of sharing mouthpieces, wetsuits, etc. with unknown persons and the issue of unknown cleaning methods. Ewww. Scuba gear is just too intimate to share unless there is no other way. Too many bodily functions occuring while diving. (That oughta convince her if nothing else does!)
Foo