mediatrix

from WordNet (r) 3.0 (2006)

mediatrix
    n 1: a woman who is a mediator

from The Collaborative International Dictionary of English v.0.48

Mediatress \Me`di*a"tress\, Mediatrix \Me`di*a*"trix\, n. [L.
   mediatrix, f. of mediator: cf. F. m['e]diatrice.]
   A female mediator.
   [1913 Webster]