Source : Webster's Revised Unabridged Dictionary (1913)

Girlish \Girl"ish\, a.
   Like, or characteristic of, a girl; of or pertaining to
   girlhood; innocent; artless; immature; weak; as, girlish
   ways; girlish grief. -- {Girl"ish*ly}, adv. --
   {Girl"ish*ness}, n.

Source : WordNet®

girlishness
     n : being characteristic of a girl