IN my opinion
The wallpaper becomes an obsession with the narrator.She's confined, and with nothing else to do she concentrates on her surroundings. In this case the yellow wallpaper. What her physician has deemed a rest cure,is emotionally any but. The wallpaper serves to capture her imagination, irritate her, and completely stress her out. Isolation is hampering her natural creativity and the wallpaper is making her a bit crazy;wallpaper captivates her imagination-
'I never saw a worse paper in my life. One of those sprawling flamboyant patterns committing every artistic sin. It is dull enough to confuse the eye in following, pronounced enough to constantly irritate and provoke study, and when you follow the lame uncertain curves for a little distance they suddenly commit suicide--plunge off at outrageous angles, destroy themselves in unheard of contradictions.
The color is repellent, almost revolting; a smouldering unclean yellow, strangely faded by the slow-turning sunlight.
It is a dull yet lurid orange in some places, a sickly sulphur tint in others.
No wonder the children hated it! I should hate it myself if I had to live in this room long.'
Yellow Wallpaper' - Charlotte Perkins Gilman
I would say that it is C sarcasm
