Which girl fits Itachi from the living?
Its going to be a long answer:
Well. Lets look at the perspective when Itachi didnt kill the Uchiha yet.
He needed some powerful, analytical, and someone who could have known that Senju were behind all that drama.
She would be his bff. More than Shisui. Therefore she must be a master in Talk no jutsu to get through Itachi's dense head and Will of Fire Propaganda.
She would have to be really influential in the clan. So someone that master all the story about them. A true Indra daughter.
She would also have to be at least Anbu level. A real prodigy.
Lets not also forget the ideology: she would have to be fully engaged to changing the world.
I guess that at this rate she would be a better Uchiha Clan leader than him.
And that would be his female bff.