Late '70s, I played in a number of games, but only one female GM. She was not very good, basically running a game so her BF could play one of the cheezyist abominations I have ever seen. In '80, she started a new game for the girls in her dorm. Yeah, all girl! Every girl complimented her on her keeping track of all the plot lines. I guess soap operas have benefits.
That said, she was up to snuff on the rules as a player and often ran the crew in my game. She shed the 'gf' role and became a dynamic player and solid GM for Traveller. Interestingly, two of the girls from her dorm game have run games I played in, both solid GMs.
Most of the early GMs were mediocre, regardless of sex. The precious few females were not much better than the Mean of the males, probably because no one dared criticize them, but none were remotely as bad as some of the males. The women GMs (years pass, all the 'girl GMs' started having kids) increased in quality faster than the average guy, usually relying on each other for friendly criticism. Guys suffered more from ego issues and got their backs up when called on rules, etc.
The only female GMs in my current contacts are dedicated to either running APs (1), kitchen table games for their kids/etc (2) or learning PF after years of 4E with the help of her parents' old OD&D crew (1). All 4 are much more open in the running of the game than most guys. The mother of the last strongly influenced my current running style, letting the players basically run the rules while I handle the world.