In Trifles by Susan Gospell, what could be a reason for the author to make Minnie Wright as an off-stage character in the play?

Although she does not appear in the play, she is the main suspect in her husband's murder and sends Mrs. Peters and Mrs. Hale to collect a few minor items for her from the farmhouse. I think Minnie represents an idea more than a person. She is the embodiment of women trapped in abusive marriages. She represents emancipation from subservience.