Given the pronounciation key on this site (
http://www.behindthename.com/pronunciation.php ) I can confirm that the German pronounciation using THIS KEY is indeed NEE-na. Note that NIY-na is not definied in the pronounciation key. It is surely not pronounced NIE-na (which is the key for "nine-na"). A famous German namesake is the singer Nina Hagen, and she pronounces herself NEE-na (There's a song from her with the lines "Ick bin die Nina, ick bin Balina, ick fühl mir prima" -- Berlin dialect, not exactly standard German).
This message was edited 10/12/2014, 8:57 AM