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]WordNet (r) 3.0 (2006):
mediatrix n 1: a woman who is a mediator