The problem with female shinobi (and male shinobi outside of the top ten) is that there are no clear cut absolute best female shinobi. For example take Konan, Tsunade, and Mei I view them sort of like I would the three pokemon starters water trumps fire, fire trumps grass, grass trumps water. In this case Mei can counter Konnans paper release with her mastery of Water, and Fire release, while Tsunade can defeat Mei with her resilience, and superior Taijustsu, while Tsunade would have no answer for Konnans paper jutsu. That's just my .02, take it of leave.