Just saw this on the Reddit thread, but there's speculation over there that Umi introduced Chizuru to another producer, and she was shot down. She's not mad when Kazuya catches walks in (which could be expected if Umi made a move on her, or meddled with her relationship with Kazuya), she looks defeated, just like after the play when the other actress was chosen.
This is all pending on what happened off screen, but I thought it was an interesting piece of speculation.