Hypernova
Warlord
Wu was the only direct ruler, all the others ruled through other official rulers. It's not just that Wu ruled "in a more traditional way" she was the only official female ruler who ruled in any way.Also, I have to say, Lu Zhi also had a large amount of control. Then, in the same ship as Cixi, you have Ci'an.
Though I will give you that Wu ruled in a more traditional way than the above. I just feel it's unfair to claim China only had one female ruler in its entire history.