I think it is a misconception that young women need female mentors - a young woman can do just as well with an excellent male mentor.
My daughter just graduated with a combined math/econ degree from a large institution. In her four years she had only 1 female math teacher and no female econ teachers (this was just how it worked out - both departments did have female teachers although they had more male teachers). When I related this to somebody at the school - she was aghast and replied what a shame that your daughter had no role model - I replied that the male teachers were her role models and that was fine with my daughter.