The speaker gives her partner an ultimatum, "me or her," and at first treats it as a plain either/or. The poem then shows why it was never that simple for him. It wasn't like picking between Coke and Pepsi. The speaker lays out two kinds of love: her own, with soft goodnight kisses, tenderness and easy happiness, and the other woman's, with late nights, alcohol and the feeling of being alive.
The turn comes when he answers "I love you." She expects comfort, but she hears the truth underneath it. If the choice was between "I love you" and "I need you," then saying he loves her means he needs the other woman. The image of her heart falling onto cracked pavement makes the pain sudden and physical.
The mood is raw and quietly bitter. The plain, conversational language and the lack of punctuation make it feel like someone talking through a breakup, working out the heartbreak line by line until the last, stinging realization.