If she speaks norwegian then she won't need an translator... swedish and norwegian are close enough that it's easy to understand (oral version, written swedish is a bit trickier for norwegians), so she will be fine.
If you're in Norway and want to go with her - then yes, I think it is a good idea. You might not be allowed in the room with her, but you showing up with her for the interview is a good sign of course. Type of questions are usually about your history, where you have been to school, if she has met your family etc. basically - any information that was in your application she should know about. She can also prepare additional proofs of communication since the application was filed, until now. Any communication, and if you went to visit her, then she should take that as well. If you went on holidays somewhere, etc.
Lykke til!
Sweden