This is an excellent statement to consider. However, to be honest, I actually think that Chopin both sympathises and pities the character of Edna, and that in the character of Edna Chopin expresses and captures many of her own frustrations with the limitations placed upon women in her time. The way that Edna feels that there is no way out of her trapped and restricted position apart from suicide is meant to make us feel sorry for her.
However, that aside, if I were to try and argue the reverse, I would want to start by looking at the various negative ways in which it could be argued Edna is presented, especially regarding her selfish attitude and the way that she practically deserts both her husband and children. Consider, for example, the way that in Chapter 37, when she is present at the latest birth of her friend Adele, she is forcibly reminded of her duties as a mother:
She was still stunned and speechless with emotion when later she leaned over her friend to kiss her and softly say goodbye. Adele, pressing her cheek, whispered in an exhausted voice: "Think of the children, Edna. Oh think of the children! Remember them."
Clearly, we can take this comment as a kind of rebuke. Adele is trying to remind her friend of the various people who are dependent upon her, and is gently pointing out that Edna's rejection of the roles that society has given her of mother and wife will actually harm her husband and children. It could be argued that it is Edna's rejection of her roles, and the way that she tries to establish a life for herself away from them, that gives her the opportunity to develop inappropriate relationships. Taking such a view would allow us to feel sympathy for Edna, but not to completely pity her, as we can see that her misery is at least partly a result of her own actions.