Characters' actions don't always reveal how they feel on the inside. We get the sense that they put on a show of proper behavior, while feeling true, unpopular feelings only on the inside. Mrs. Mallard's response to the news of Mr. Mallard's death simultaneously proves how different she is from other women and yet how she seems to truly, honestly mourn her husband:
She did not hear the story as many women have heard the same, with a paralyzed inability to accept its significance. She wept at once, with sudden, wild abandonment, in her sister's arms. (3)
The narrator says here that "many women" would respond with "paralyzed inability" but Mrs. Mallard is unique in crying right away. While acting so differently should make other characters realize that perhaps something is out of the ordinary, the fact that Mrs. Mallard displays her grief so "wild[ly]" seems to make them think she is devastated at the loss of her husband.
Similarly, when Mrs. Mallard is locked up in her room crying, her sister Josephine thinks Mrs. Mallard "will make [her]self ill" (17). Really, though, Mrs. Mallard is experiencing an epiphany and a call to freedom; if she is making herself sick, she's sick on the euphoric feeling of no longer being attached to anyone else.
Not only do we not know that much about the characters in this story, we don't even know all of their names. Names serve, then, as reminders of how the characters stand as ciphers or how Chopin leaves it up to readers to fill in their gaps.
While we know Mr. and Mrs. Mallard's full names (Brently Mallard and Louise Mallard, respectively), we only learn half of the other characters' names. Mrs. Mallard's sister is only referred to by her first name, Josephine, while Mr. Mallard's friend is only referred to by his last name, Richards.
Perhaps, in these incomplete names, we're seeing some sort of connection to domestic and public spaces. Calling someone Josephine, a first name, indicates intimacy and the idea of knowing someone well. You use first names in a family or domestic situation. In contrast, calling someone Richards, a last name, indicates formality and distance. A man would use his last name in business settings or outside of the home, in the real world.
As for the married couple's last name – "mallard" is a kind of duck. Popular opinion holds that mallard ducks mate for life, but scientific research seems to indicate that mallards are actually more fickle (source). Potential fickleness juxtaposed against a long-term relationship actually seems to fit Mr. and Mrs. Mallard pretty well.
The impact of Mr. Mallard's first name, Brently, is less clear. Traditionally, Brently means "hill, mount" (source). Maybe this is a reference to the alive outside world that Mrs. Mallard only looks on from her window. Any other ideas?
Finally, the two sisters, Louise (Mrs. Mallard) and Josephine, both have first names that are feminized versions of male names. In both her first and last names, then, Mrs. Mallard is identified according to some male original. She's taken her husband's last name, her first name originated as a boy's name, and people refer to her as Mrs. She can't escape her status as a woman defined by and in relation to other men.
For much of the story, we're treated to Mrs. Mallard's thought process as she copes with the experience of her husband's death and starts almost instantly to get excited about the potential freedom that can bring. We learn most about Mrs. Mallard's character from witnessing her move through a series of thoughts about her husband's death. In this moment, she seems to abandon love for selfhood:
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! […] 'Free! Body and soul free!' she kept whispering. (15-16)
Mrs. Mallard rejects grand concepts and loving connections because she's experiencing the "strongest impulse of her being": freedom. Being free suddenly matters to her more than anything else. And, while this epiphany seems sudden, it appears like she's been waiting for this feeling a long time, and just didn't know how to put it into words.
Up until she got the news, she says, she'd been worried about how much more life she had to live (19). Only with the idea of freedom made possible (granted, through a tragic event), does she start getting excited about the rest of her lifespan.
Even as Chopin presents us with Mrs. Mallard's thoughts, though, it's up to us readers to decide what kind person she is: so callous that she can put aside her husband's death easily; or so deeply troubled that it would take an event of this magnitude to make her feel anything.