I can understand it on a warrior type like Wonder Woman and Huntress, though. Long hair is easy to grab, it's a real liability in a fight. You don't want that weakness. With "magic" or whatever characters like Starfire, Zatanna, etc., it hardly matters as much.
With She-Hulk, though, unless Jessica Walters is going to sport a wrestling cut while lawyering, she could just do with a pixie cut. I could handle pixie cut She-Hulk. And Power Girl already has short hair.
And I will concede that I like a viking braid on Valkyrie and a tight ponytail on Black Canary.