In the 70s DC had a back up series in the Lois Lane book, Rose and the Thorn. Rose Forrest was a blond haired, blue eyed woman who ran a flower shop. She lived in Metropolis, and pretty much stayed out of everyone's way. Her Father was a detective murdered by a criminal organization called The 100. His death caused something to break in Rose. In the evening after she would fall asleep, she would rise and wear a brown haired wig and green contacts, and wage war on The 100 as The Thorn. While not a flagship female character, I think the Jekyll/Hyde situation would make for an interesting film.