If you're struggling to create a thesis for a topic, you're likely struggling to envision the body paragraphs as well. Many students find that building those ideas into their thesis helps them to better plan for their paper. With that in mind, I would suggest a thesis that both directly addresses the topic of feminist criticism and weaves the support into the statement as well. Something like this would work:

The Story of an Hour is an example of feminist literature through the emotional oppression of Louise Mallard, the loss of her own sense of identity within her marriage, and the brief joy she experiences when given a taste of the freedom that independence could hold.

The first body paragraph would discuss how Louise exists in a marriage that brings her no happiness. It is noted that she has feared that her days on earth might be long, indicating that she finds no joy in her married life. When she first accepts the news, she accepts it willingly—gladly. She weeps in an outpouring of emotion that has been bottled up within her for years.

Your second body paragraph could then focus on all the ways Louise is reduced to being simply a wife. She is introduced as Mrs. Mallard and isn't given a first name for most of the story. It is also noted that "she had loved him—sometimes. Often she had not." Within her historical context, Louise is expected to simply exist for the rest of her days, supporting her husband and caring for his needs while sacrificing any hope of joy she holds for herself.

The final paragraph would then look at how Louise experiences great joy at the thought of being able to make her own choices, no longer living for another person's comforts:

There would be no one to live for her during those coming years; she would live for herself. There would be no powerful will bending hers in that blind persistence with which men and women believe they have a right to impose a private will upon a fellow-creature.

She takes time to gaze out the window, noting the signs of new life all around her. And she believes that this opportunity is her chance for a new life that she can claim all for herself.

Of course, none of this proves true as she has simply received poor information. The loss of the freedom she believes she'd been granted is too much for Louise, and she dies upon seeing her husband. Thus, the role of patriarchy in this story proves crushing to a woman who feels marginalized by her lack of opportunities because of her gender.

Kate Chopin's "The Story of an Hour" is considered feminist literature since its narrative treats the central character, Louise Mallard, as a fully realized person with desires and deep feelings that conflict with patriarchal power and its repression of her self-assertion. 

Feminist Literary Criticism examines a text from the perspective of its perpetuation or its rejection of patriarchy and its ideologies. Kate Chopin's story of Mrs. Mallard's one hour of freedom defines the repression of a woman under patriarchy and the potential of this female outside of such a restrictive structure of principles and ideals. Therefore, a good thesis statement for an essay that considers the interpretive question about why Kate Chopin's story is considered feminist literature will address the idea that Mrs. Mallard is repressed under patriarchy, but after learning of her husband's death, she entertains new possibilities for the expression of her own desires.

Here is an example of a thesis statement:

For one hour Mrs. Mallard, who has suffered from repression in a marriage that is male-dominated, feels a growing sense of autonomy and worth as she has been given independence and control of her life by the news of her husband's death.

Support for this thesis can be formed from the ideas of the passage in which Mrs. Mallard whispers, "free, free, free!" as she feels her blood "coursing" and "warmed" in her. "[E]very inch of her body" relaxes as she becomes aware that she is no longer trapped by her marriage to Brently Mallard. It is only then that she considers the future as she feels such "monstrous joy" brought by her realization of freedom from patriarchal oppression.

"The Story of an Hour"  by Kate Chopin shows a different point of view about marriage.  In the time of the story, married women were not masters of their fate.  They relied on their husbands for financial support and were expected to do a great deal in return.  As in the case of Louise Mallard, money was not the issue.  Since Louise was ill, she had been told  what to do and never left to make choices for herself. 

The only way that Louise would ever be in charge of her own life is if her husband died.  This is why after her initial grief that she seems elated that now she will have her freedom to do as she pleases. 

Evaluating the women's plight and looking at life from a female perspective is feminist literature. In her writing, Chopin was committed to giving the woman in literature her own perspective. Her heroines would have lives beyond the male view of life. Louise Mallard would have her few moments of freedom:

There would be no one to live for during those coming years; she would live for herself. There would be no powerful will bending hers in that blind persistence with which men and women believe they have a right to impose a private will upon a fellow-creature...

Potential thesis statements:

In "The Story of an Hour," Louise Mallard finds unexpected freedom, no matter how transient. 

Kate Chopin provides a few minutes of freedom from male oppression in "The Story of an Hour."

Louise Mallard slips the bonds of male oppression in "The Story of an Hour."

Louise Mallard recognition of her unhappiness gives way to the "joy of freedom."

Louise Mallard has been subjected to masculine oppression through her doctor to her husband.

"The Story of an Hour” by Kate Chopin, considered an example of early feminist literature, illustrates a woman’s reaction to the end of an unhappy marriage and the beginning of a new life on her own.

In "The Story of an Hour" Chopin  questions the institution of marriage in a cleverly subversive way.