There’s a part in the game where she gets confused over the word retribution, and misuses it twice. The simplicity in how she speaks makes the message that much more relatable, too. It not only emphasizes just what exactly it is she’s feeling and how she’s responding, but also the “loop” one can get into when they suffer from depression.
The repetitive dialogue that runs through Sayori’s brain, accusing her of being a failure, that she should just sleep forever, that all she does is make others sad by failing, is a disturbingly accurate representation of how one’s brain works when they’re depressed.