Although Observers were genetically programmed to be male, occasionally a few females occurred. Their ability to see all timelines and anticipate future events before they happened — combined with their total lack of emotion — made them fantastic secretaries, receptionists and personal assistants.
I dunno, am I the only one who noticed all those Robert Palmer girls in little black dresses cast as the Massive Dynamic secretaries over the years? It just bolsters my theory that none other than William Bell was behind the creation of the Observers. They were right under our noses all the time.