The Collaborative International Dictionary of English v.0.48:

Maidenliness \Maid"en*li*ness\, n.
   The quality of being maidenly; the behavior that becomes a
   maid; modesty; gentleness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

maidenliness
    n 1: behavior befitting a young maiden