Rukia :
-She is the reason why Ichigo and friends invade the SS.
-She is the reason why Ukitake and her comrades,went against the law of the SS,in order to save her.
-She is the reason why Yoruichi needs to go back to SS,and accompany Ichigo,to be able to save her.
-She is the reason why Renji wants to kill Ichigo at the beginning.
-She is the reason why Byakuya who's very loyal to the law of the SS,acts against it by saving her from Gin.
-She is the reason why Ichigo and Renji wants to become stronger.
-She is the one who made Hanataro sacrifice himself by trying to face Byakuya alone.
-She is the main target of Aizen for having the hougyoku.
-Huge part of the story in SS arc,was about her,being a friend of Renji,her memory about Kaien,her words about Ichigo that he heard from Hanataro,gave him more determination to stand up and continue fighting.
-She is the reason why Ichigo is trying to stay alive during his fight with Kenpachi.
-She is the reason Ichigo gained his bankai in just two days.
-She is the reason why the hallow Ichigo didn't manage to control Ichigo during his fight with Byakuya.
-She is the reason why the rain in Ichigo's heart had stopped.
Inoe :
-She healed their injuries after the battles.
I guess no one would argue who's the female protagonist here.