This is my top 20 most played female vocalist inside my all time top 100 based on my last.fm overall (band with female vocalist doesn't count)
1. Adele (no. 18 overall)
2. Sade (no. 20 overall)
3. Alanis Morissette (no. 26 overall)
4. Lily Allen (no. 31 overall)
5. Feist (no. 35 overall)
6. Avril Lavigne (no. 41 overall)
7. Ellie Goulding (no. 45 overall)
8. Bjork (no. 47 overall)
9. Sia (no. 51 overall)
10. Rihanna (no. 54 overall)
11. Madonna (no. 56 overall)
12. Katy Perry (no. 60 overall)
13. Esperanza Spalding (no. 62 overall)
14. Mariah Carey (no. 63 overall)
15. Beyonce (no. 64 overall)
16. Dido (no. 68 overall)
17. Alicia keys (no. 79 overall)
18. Pink (no. 89 overall)
19. Britney spears (no. 92 overall)
20. Zee Avi (no. 93 overall)
Hope you find your faves there