Niamh is an ancient Irish name that was originally a term for a goddess; rich in legendary associations. In Irish myth, one who bore it was Niamh of the Golden Hair, daughter of the sea god, who falls in love with Finn's son Oisin/Ossian and takes him to the Land of Promise, where they stayed for three hundred years.
Niamh is in the Irish Top 30, and is also well used in England and Scotland. Here, the phonetic Neve would undoubtedly prove simpler, if less intriguing. But if you're worried about pronunciation, just keep in mind Saoirse Ronan and Sinead O'Connor--it never stood in their way.
Niamh is currently Number 21 in Northern Ireland, 30 in Ireland, 39 in Scotland and 81 in England and Wales.
The English version Neve is the name of actress Neve Campbell, for whom it has family connections, and the daughter of Conan O'Brien.