Winston sees this woman as a symbol of freedom. Party members never sing, but hearing her song through the window of his rented room fills Winston – and soon, Julia – with hope for the future. What is this hope? That the proles will become cognizant of their plight and rebel against the Party. After all, Winston reasons, the Proles constitute the only group capable of success because of their sheer size (85% of Oceania population). Unfortunately, as Winston and Shmoop note, the proles aren’t smart enough to get their act together. Thwarted again.
But that’s not all. Winston and Julia also acknowledge the Prole woman as a symbol of reproductive virility, and thereby, hope for the future. They see her as "beautiful" because of her wideness, largeness, and toughness – all indicating her ability to give birth to future generations of rebels intent on overtaking the Party’s rule.