Welp, looks like nothing to worry about a rival...she only seems to care about the state of the club and not Sempai.
Also, I could have sworn we'd seen other art club members in past chapters...but it was just as they were leaving the club for the day. Seems like Sempai stays longer than any of them...and that's when Toro and the other Gyarus usually visit him.
@whoamiagain No, she's not. She acts like Sempai isn't serious when we know damn well better how serious he is about his art.