Many Maori names include (and often begin with) /ng/, which is NOT pronounced just like /n/. It is pronounced just like the /ng/ in "sing", only without a vowel in front of it. The back of the tongue is pressed against the roof of the mouth and the vocal chords are sounded.
Also, I'm not fluent in Maori, but I lived in New Zealand and studied it informally. I'd be very surprised if the "i" was pronounced like the word "eye". The closest transliteration I would use would be NGEE-la.
I can't find a meaning for Ngila, but I found Ngiha at http://snipurl.com/d6my
, a scholarly collection of Maori names. It may be a variant, or it may be completely different. I'm not sure. In fact, I can't find Ngila as a Maori name anywhere on the internet other than in reference to Ngila Dickson (the costume designer). It's possible that the information is simply not on the internet; alternatively I suppose her parents might have simply made up a name that "sounded" Maori. However, I'm inclined to believe that it's a real name that I just can't find the information for. There's no good resource for Maori names available anywhere (even in print).
"Blue tinted individuals who go about armed to the teeth and quoting twelfth-century poetry are not easy to comprehend." ~ Lloyd Alexander