Glaspell's "Trifles" presents a wife, Mrs. Wright, who is isolated from society and suffers under the dominance of her husband. This is somewhat mirrored by her "peers," the two women who discover the wife's motivation for killing her husband.
Living in a patriarchal society, Mrs. Wright is kept at home and isolated, and is not even allowed a telephone. Society dictates the woman's role in the marriage, and her husband, apparently, makes sure she stays in her role.
The two women who discover her motivation are laughed at by the men who are officially investigating the death of the husband. The men find no important evidence, however, while the women uncover evidence of what must have made her snap, so to speak: the body of a pet bird. Apparently, the singing bird was a small element of joy in Mrs. Wright's life, and when the husband killed the bird, she killed the husband.
What are mere trifles to the men in the play--the bird to the husband and kitchen details to the investigators (anything the women are interested in, for that matter)--are worth killing for to Mrs. Wright, and provide the full picture of what went on and why to Mrs. Wright's "friends."
The play highlights the low status of women in society and is definitely written from a feminist point of view.