In the story "the yellow wallpaper" how does the reader know that the narrator's mental state has begun to deteriorate?

The narrator’s mental health hinges not only on whether she has work to do, but what kind of work it is. She wants to write and isn’t allowed, something that “does exhaust her a good deal” (3). The subtle undermining of her confidence as a writer doesn’t exactly help to repair the damaged relationships she shares with her husband and her sister-in-law, sending her further into a frenzy of paranoia that leads to her mounting obsession with the design of the paper on her bedroom wall.