In NZ, why do Maori's & Pacific Islanders generally not like each other?

When I was at a multi racial school in Auckland, everyone got along & there was no racism, but Islanders & Maori's never spoke to one another. My older sister said they hate each other & when she was out on the weekends there was a lot of violence between them at nightspots, etc. Why? One theory I heard was that back then (in the 1980's) there was a Government department established to help both Maori's & Islanders buy their first home & Maori's were angry it wasn't just for them only as why should immigrants be given the same rights as them. I think there must have been other reasons than that though. I wonder is Islanders do better educationally & have a lower unemployment rate than Maori & maybe there was resentment over that? Even today I notice you rarely see Maori's & Islanders together as friends or lovers, yet it's quite common to see white people with Maori friends or partners. Not really that common for white people to get together with Islanders though, I guess their culture is very different, whereas alot of Maori live the same lifestyle as Pakeha (whites) & aren't into Maori culture at all.