In The Yellow Wallpaper... Is the narrator reliable or unreliable? Can we believe everything that she says? Why or why not?
This is a deliciously beefy question! Thanks for asking!
The answer is a tripartite combination of perspectives. Through the eyes of the main character, the first perspective, the argument is completely valid. She is a woman suffering from an extreme case of post partum depression. Although it is arguable to say that she is not in a "right state of mind", it is also safe to affirm that (within her circumstances) her fears, tribulations, and anxiety are to be considered as true and worthy of our compassion. She actually sees these things. She really feels them, and she really accepts them as true. Therefore, she is suffering, battling and trying to control a situation that is entirely true to her. We are not in her shoes, so we could never have a right to say that she is wrong.
The second is the perspective of the secondary characters such as her husband, her doctor, and such. They are the ones who truly take her for a mild case that can fix itself. They do not consider her needs, nor know what the causes are for her behavior. Hence, they are the lesser perspectives as they really do not step up to try and solve the problem. Hence, she is still left out there with no other choice than to continue her path toward insanity. The secondary characters simply do not have a clue.
The third and final perpective is that of the reader. We could sit and say she is crazy, depressive, and dellusional. We know that there are no beings transforming in the yellow wallpaper. Yet, we are witnesses of her pain and, as a society, we must understand that her pain (despite of her hallucinations) is real. Her desperation is real, and so is her lack of control. Hence, if we look at the question from a deeper point of view, her argument would be completely acceptable.
It would take a very shallow mentality to not believe what she has to say. This is because we are expected (as readers) to cathartically and vicariously experience the feelings and experiences of the main character. Therefore, we are there with her in her struggle. As a result, we should agree with the main character in that her worries and fears are worthy of attention and that, in her mind, they are real, indeed.
This narrator is an unreliable interpreter of reality. She believes whole-heartedly in what she sees and experiences, and these things are very much real in her head, but that's not the same thing as them being true in a more objective sense. To say this, I think, does not belittle her; it is, simply, true that she is not a reliable source of information about her own condition or much else. The narrator believes that her health is improving; in fact, she comes to believe that the wallpaper is helping her to get better. However, we can tell from the claims that she makes about the paper—namely that there is an outer pattern that entraps a desperate woman who creeps around and wants desperately to escape her confines—that she is not getting better but worse.
Further, the narrator seems not to be aware even of her own behaviors. For example, she mentions how the children she believes lived in the room before her were so violent, taking chunks out of the bedstead with their teeth, and then a few lines later, she gets so mad that she bites the bed. She talks about the women she sees creeping in the garden outside, and then she reports that she never creeps by daylight. What begins as postpartum depression quickly turns into an illness much more dire, and she is so deprived of stimulation, other than the wallpaper, that she becomes obsessed with it. She's clearly an intelligent woman (based on her vocabulary alone), but her mind has been damaged, ironically, by the very "treatment" intended to cure her. This is not an indictment of her but of her doctors, including her own husband, and her society. She is, nonetheless, an unreliable narrator whose words we cannot take at face value.