Has she ever been to D.R.?
i like Bani. I have been several times in my adventures in D.R. There are people on streets but they are all minding their business or working (not buscando like you see in the tourist areas). There several beaches, villas, piscinas, ranches, within driving distance. The colmados and pool halls are always a good time. Everyone also tells me the best dulces are in Bani.
Bani is very low key and quiet.
If she is a city girl she might get bored there. I would do something like spend the weekend in Santo domingo, hang out with the fam during the week, then spend the weekend i santo domingo again.
Dominican Families are incredible hosts, almost too great because they will bend over backwards to entertain you. I recently went with my best friend to see his family. We didnt pay for a meal in the 11 days there because someone always had a sancocho, chivo, or churasco ready for us. i felt i needed a break every once in a while and thats why i made sure i had alternatives when i needed some space.
Has she ever been to D.R?
will they be staying with his parents?
or at hotel/resort?
are they teenagers? early/mid/late 20s?
If she is staying with the family you have to first remember the living conditions in D.R. are different. We take things for granted in the U.S. like always having running water, power, air conditioners, etc. I am sure they have all of that but even the nicest houses and neighborhoods run into issues.