Yua Sakurai is an anime-original character.
She is a model who has had some singing experience, but due to an accident, has since been afraid to sing.

As a child, Yua liked singing, but no one would listen to her. Amu Hinamori agreed to stay and listen. After episode 86, she was able to sing freely.

http://shugochara.wikia.com/wiki/Yua_Sakurai