Random Thoughts.....What Are You Thinking?

Cia only seems like she is crazy because she represents the "evil" in the heart of herself and Lana.

Really they are both the same person. It is actually because of Lana's obsession with Link that the "crazy" is pushed into the "evil" side which is Cia.

In fact Lana's obsession with Link is SO strong that EVEN with her heart split into "good" and "evil" parts, she still exhibits a longing to be with Link, which you can see in the cutscenes for the battle with the Deku tree when Proxy and Impa indicate they must find the Princess, and again in later battles when she mentions that Link and Zelda must continue their lives together.

The last example occurs when Cia has been rescued from the control Ganon had over her, and oddly enough she does not exhibit the same longing that Lana does, in fact she seems to be more mature about the situation and while she does like Link, she instead focuses her energy on helping Lana be able to get over Link.

Any of her "crazy" was simply Lana forcing more of the darkness, the bad feeling and negative energy into her with her uncontrolled feelings for Link.