The Idolmaster (anime)/Headscratchers

• In the last episode of the anime, Ritsuko go on stage with the girls to sing the song "Itsumade mo, Dokomade mo", wich is nice and all, but it doesn't explain why was she wearing a stage outfit identical to the one of the girls are wearing in that moment? Early in the episode, she's clearly wearing her suit. One could say that she wore when she was proofing it, but she wouldn't be wearing it after the girls were already on stage. Of course, the Producer or the President, or even Kotori could have delayed her or something, but since nothing is shown onscreen, or even implied, it just comes as a little too convenient to not break the Suspension of Disbelief.