If you're looking to find her highest pitch, listen to:
-"Wait & See"
-"Time Limit"
-"This One(Crying Like A Child)"

In "Wait & See", the highest vocal is at the beginning when her voice fuses with the guitar and right before the bridge (I think that's what it's called). And in "Time Limit", it's before the dance break. In "This One(Crying Like A Child)", it's during the bridge. When she's singing, "A hundred .jpeg files filling up my hard drive.." the vocal branches off of "drive" and begins to get higher.

For her lowest range, try her English work. Most of it is in a lower tone than her Japanese. A good example would be "Devil Inside" & "Hotel Lobby".

Hopefully this helps you on what you're trying to do.