So far as skiffle was concerned, I don't think it was a matter of whether or nitr it was respectable. (Actually it was, as often as not.) I'd say it was more a question of motivation. And that wasn't basically about fame and fortune, it was primarily a way of showing off, and girls had other ways of doing that, which didn't involve learning three chords on a guitar.

There were girls in skiffle but relatively few. (Notably "Nancy Whiskey" - born Anne Wilson - with Chas McDevitt) And if there were any all girl skiffle groups I never heard of them.