The Collaborative International Dictionary of English v.0.48:

nagger \nagger\ n.
   Someone (especially a woman) who constantly finds fault.

   Syn: scold, scolder, nag.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Nag \Nag\ (n[a^]g), n.
   A person who nags, especially habitually; called also
   nagger.
   [PJC]

WordNet (r) 3.0 (2006):

nagger
    n 1: someone (especially a woman) who annoys people by
         constantly finding fault [syn: scold, scolder, nag,
         nagger, common scold]