One of the worst parts of the rape scene was seeing Rumi crying while watching it being filmed. The Fridge Horror comes in when you're given time, near the climax of the movie, to remember that scene: you realize that Rumi may already have been unstable and delusional but this and the racy photo shoot were the things that pushed her permanently over the edge.
Or even worse, if Rumi was already delusional, she thought she was seeing herself getting raped. It gets worse when you consider just how strongly she protested Mima doing it in the first place and how it connects with the conclusion of the Show Within a Show.
Some of the the lyrics from CHAM's song at the beginning of the film could have given Me-Mania... ideas.
In the climax, most of the chase scene is a delusion of idol-Mima chasing the real one, gliding and hopping like a fairy. Except the Glamour Failure reveals it's a Rumi chasing down Mima, visibly panting and running in real life. First, props to her for having the stamina to keep up with Mima who still has her dancer's training and second, she was able to keep up with Mima long enough for the gliding delusion to happen. The glamour is also unsettling with idol-Mima having a Slasher Smile that we've never seen on the real person.