As portraits of all the royal personages from the 1870's and 1880's are well documented, this is more likely a woman of prominence, in her own right or as the wife of a notable person. This portrait was made to commemorate some important occasion, as indicated by the many leis.
As Bruce Erickson has kindly observed, the leafy lei, the maile, "is given when the giver wants to bestow the highest honor. Maile is a forest vine which holds its fragrance even after the leaves dryĆ ."