Quote 4
What could love, the unsolved mystery, count for in face of this possession of self-assertion which she suddenly recognized as the strongest impulse of her being! (15)
Can love really just be cast aside like this? Here, Mrs. Mallard reduces it to the "unsolved mystery" and presses on, casting aside her feelings for her husband and however many years they've been married for this freeing idea of "self-assertion." It's hard to say if she's crazy with grief, if she's in denial, or if it's possible to be unhappy in a purely regular marriage. You know, like Don and Betty Draper in Mad Men.
Quote 5
She knew that she would weep again when she saw the kind, tender hands folded in death; the face that had never looked save with love upon her, fixed and gray and dead. (13)
One could argue, in a moment like this, that Mrs. Mallard is putting aside the much larger grief that her husband's death has caused because she understands that she'll "weep again" when she sees his body. This makes it sound like she's trying to concentrate on freedom and other ideas that will distract her from her grief. Of course, this idea seems to be undercut by the other passages describing just how much this newfound freedom means to her.
Quote 6
There would be no one to live for during those coming years; she would live for herself. (14)
The parallel structure of this sentence almost seems to imply that Mrs. Mallard is "no one"' there's "no one to live for" so "she [will] live for herself." In each part of the sentence, the verb used is the same, so "no one" and "herself" occupy the same relationship. Either Mrs. Mallard thinks that "no one" values her, or she's suggesting that it's only possible for her to be "herself" if there's no one else around.