[quote="Kopa23"]If you really love someone, you forgive what they do, whatever that is... She loved Scar from what we see in the movie, so we can guess that in her eyes, Scar was the one true King.[/quote]
^ This
[quote="PrincessKiara"]I think Zira believed that Scar deserved to be king instead of Mufasa, and the only way for Scar to achieve his true rank in the Pride, would be to kill his brother.
We`ve seen how cold Zira can be to her own cubs, so I think she knew what Scar did and thought it the right thing to do. In SP, Zira is portrayed as quite power-hungry, similar to Scar, both are characters who`d do anything to get the power.
So yes, I believe Zira knew what Scar had done to become king, and thought that he should have been king all along. She was after all extremely loyal to him.
On a side note, I too believe Zira is insane.

EDIT: I just thought of something.. I don`t see it as very likely that Scar would tell anyone that he had killed his own brother to get the throne. BUT if he and Zira were in fact mates, and in love, it is possible that he told her. It could be that they told eachother everything.. And maybe Scar saw a lot of himself in Zira, and chose to confide in her.[/quote]
And this ^
But I think however, Zira would have forgivin Scar for what he did, so she really didn't care, but when Simba killed Scar, she might have unforgivin him.