Chieri is very conflicted regarding her role as centre nova.
On one hand, she is very happy and greatful, being able to hold such a unique position.
But at the same time, the position is partially luck, so she feels that she doesn't quite have the skills or popularity or something to live up to the name.
Because of this, she doesn't always perform as centre nova. With the position, nobody can stand in for her, meaning its a normal senbatsu or kenkyuusei performance, but there are no rules saying she has to be at the front for every performance either.
Despite this, she's looking forward to the day where she feels confident enough to lead and protect every one as a proper centre nova.