Cheza is the Flower girl, she apparently is made of flowers. She and Kiba have a close bond, he can always find her no matter how far away she is. She is only alive for a short time, before which, they must find paradise.

[If you haven't ruined it enough for yourself keep reading - Contains Images]

[Spoiler]

How does it end for Cheza?
She turns into seeds.

Does she "die" alone?
No she's not alone, Kiba's with her.