In analyzing Duffy's poem, one sees that the speaker is a child who is seeing pictures of her mother. The ability to see the mother in pictures as a young woman, before pregnancy and before motherhood, causes the daughter to speak in "Before You Were Mine." The poem is a recollection of what her mother must have been like when she was a young woman.
"Before You Were Mine" deals with a reality of how women understand one another. Prior to motherhood, there was an identity that the woman possessed. It involved going out to dances in the evening, hanging out with friends, and having to take some level of punishment for spending late hours away from home. With the line, "The decade ahead of my loud, possessive yell was the best one, eh?," it becomes clear that the speaker of the poem can see that there was a point where her mother was truly happy. She describes the shoes that her mother wore as a young person as "relics" and the teaching of dance steps as almost a portal to reconnect with a past that disappeared with the demands of motherhood.
This "glamorous love where you sparkle and waltz" is part of an identity that will never be had again, something permanently changed with the responsibilities and demands of motherhood. It is in this where the poem seeks to articulate the condition of women. It is one in which daughters recognize their same traits in their mothers, where a child holds understanding about their parent. However, it is a melancholic condition in which the child understands that their own presence means the end of one aspect of their parent's life. In "I wanted the bold girl winking in Portobello, somewhere in Scotland, before I was born," this realization impacts the speaker. It is this condition in which the poem is a melancholic ode to that which has passed, a time that existed "Before You Were Mine."