Despite the fact that the narrator initially feels that the wallpaper is disgusting and frightening, she eventually comes to feel compassionate toward the woman she believes is trapped behind the pattern of the paper (before she believes it is actually herself). As she descends into mental illness, she strives to help the trapped woman:
As soon as it was moonlight, and that poor thing began to crawl and shake the pattern, I got up and ran to help her.
I pulled and she shook, I shook and she pulled, and before morning we had peeled off yards of paper.
And then when the sun came and that awful pattern began to laugh at me I declared I would finish it today!
It is clear that the narrator is also removing the wallpaper because she feels it is mocking and belittling her by laughing at her. Both the feeling of being trapped and the notion the wallpaper is laughing at her are indicative of her relationship with her husband. She is trying to save herself, essentially, by freeing herself.
The narrator notices that the front pattern of the wallpaper forms bars which the trapped woman attempts to climb through but fails each time. The woman’s attempts heighten at night and she even shakes the bars to free herself but each time she is unsuccessful. The narrator, who believes she is the same woman trapped behind the wallpaper, wants to free herself. She empathizes with the woman’s situation and imagines her humiliation for having to creep during daytime. She also thinks that nobody can escape past the bars alive as anyone who does gets strangled and so the only way she could save the woman is by destroying the entire wallpaper. The wallpaper was her only impediment to freedom and so she decides to permanently destroy it to ensure she would never be trapped behind it again.