There is no better true test of relative upper body strength than the pull up or pull up variations.
A lot of females sturggle to do pull ups for many reasons but one of those reasons is lack of core strength.
Genereally most females will do pull ups with their feet tucked behind as seen in this pic below.
This is an OK position but in doing this you basically take your core out of the pull up and it can also be painful for anyoone with a lower back issue.
A much better position for your feet and lower body is to have your toes pointed out in front of you.
The feet can be out at an angle pointing down or out in front at 45% like an L either version is fine.
This is a much harder and more effective way to do pull ups and will engage your core making this a much more full body exercise.
If you are a female looking to improve your pull ups and upper body strength check out my Pull Ups For Women program.