In the story "the gift of the magi", how did della's choices and interactions with others develop the plot?

Della's interactions with others helped move the plot along by creating new scenes with different decisions and choices she had to make. When she talked with the hairdresser about cutting and selling her hair, the moment makes the reader want to know what happens next with Della and her hair.
When her husband comes home, the readers want to know how he reacts to her shorn head. Every interaction helps to move the plot along and keep the readers engaged.