For lurkers, Ann Wilson of Heart is widely considered one of the finest female rock vocalists of all time.
I remember idly listening to a CBC radio interview with Maureen Forrester in the '70s. The interviewer asked who she liked to listen to in her spare time, she replied, "Ann Wilson". The interviewer didn't follow up, obviously had no clue... I laughed.
I've always liked Heart, though Nancy Wilson has more talent, IMO.