The ability to do a pull-up is not entirely dependent on your level of fitness, so even very fit women may have trouble doing pull-ups.
Why is it hard for women to do a pull-up? Here's where to start
I Gave Myself Six Weeks To Master A Chin-Up — Here's What Happened
Below the Bar - The New York Times
Women can do pullups; here's the secret
Scared Of Pull-Ups? Here's How Guys Can Go From 'Zero To Hero' & Do Their First Ever Pull-Up
How to get your first pull-up (Women Friendly)
Do Pull-Ups Help Deadlifts? (Yes, Here's How)
How to Get Your First Pull-Up
Do Push Ups Help With Pull Ups: Here's Why Not - Inspire US
Can't Do a Pull-Up? Here's What Your Body Is Trying to Tell You, Livestrong.com
Chinup Vs Pullup—The Difference And How To Work Up To Both