First of all, Dominica is a resort island - withouth the resorts. Its a good idea for your girlfriend and family to come with you during break time so that you can all enjoy it together (without being really stressed and time crunched). There are several water falls to visit, many VERY nice secluded beaches (that most students don't even know about), several good hikes to interesting places, rain forest tours, River Tours (ie. Indian River Tour), the Carib Territory, great scuba diving, a "swim with the dophins" center, and several other things. You may want to check out www.avirtualdominica.com for more ideas on what you can do and where they can stay. A very nice hotel in Roseau is the Fort Young Hotel (look it up on the internet). Its very nice, but the only problem is that it is in Roseau where there are no beaches. The beaches are around the school and mostly north. SO it depends on what they like to do. St. Maarten isn't very close, but can be reached by an island-hopping plane easily. Barbados and Martinique (the French Hawaii) are close and also accessible by plane. But you can also take a nice ferry there for about $60 roound trip. Get you know a good transport driver once you are here. They are very friendly and will always put together for you if you are interested.
Hope this helps!
RUSM 2006 Graduate