[ni:v] or [niəv]
Native Irish pronunciation: [ˈnʲiəvˠ]
In Irish, <mh> (and <bh>) can make a /v/ sound.
I have heard many mispronunciations, some of which are listed below!
[ni:m]
[ni:f]
[ˈnima]
[nɪm]
[niˈjam]
[niˈjame]
[sni:v]
[esni:v]