Beyonce is my fave and she is a legend/icon/etc. and she is definitely important, but nowhere near as important as those I named. Her influence is going to be huge, but as of right now, it is only moderately visible.
In history:
Aretha,Whitney,Ella Fitzgerald,Diana Ross,Tina Turner,Mariah Carey,Janet if you count biracial people.
Most of the female rappers from the '80s and '90s
Aaliyah would be a good guess too but that might push it since a good part of it has to do with her untimely passing