I vaguely remembered that there where plenty women driving at Le Mans in the '30s and according to this I was right:
http://en.wikipedia.org/wiki/List_of...omen.27s_teams
And apparently there was in earlier all woman crew winning their class in 1974, the Chevron driven by Beckers, Laurent and Fontaine.
And a second one in 1975, making it two woman crews winning the class in 1975.