In addition to the Makiki location of the Contemporary Museum, there is also a
downtown annex in Honolulu (possibly the First Federal Bank building, but
double check).  The University of Hawaii at Manoa also has an art gallery that
exhibits student works and can be surprisingly good.  The art scene in
Honolulu is quite active - I suggest that your friend checks a publication
called the Honolulu Weekly - it's a great resource for more non-traditional
exhibitions.
- Malia