Which LDS FHC(Latter-Day Saints Family History Center) do you visit?
If on any of the islands, volunteers at a LDS FHC of your choice should be able to assist you in regards to Polynesian name history patterns.
If in the States, any volunteer at a LDS FHC of your choosing can assist and direct you to resources regarding Polynesian name history patterns. http://www.familysearch.org/Eng/Library/FHC/frameset_fhc.asp...
Find a Family History Center near you...
"Omeka Leomiti Asa was born with the last name Masala (names of birth parents are unknown) and raised by her grandmother Leiu Leomiti."
--"...grandmother Leiu LEOMITI.". Is not LEOMITI one of the parents' name? the unknown mother's surname? And if LEOMITI is a married surname, do you know Leiu's maiden name?
I've searched for MASALA as a forename and surname -- IGI/Southwest Pacific (No Matches). Are you sure of the spelling?
Let us know of how you fare on your first journey of many in genealogy - <G>.