Fr. Michael Monshau, O.P. on the titles of Our Lady:

In many ways, expressions of love for Mary rank among the products of Catholic devotional spirituality at its best. As Our Lord assured us from the Cross, Mary is our Mother. Pope Benedict XVI wrote in his encyclical Deus Caritas Est, "Mary has truly become the Mother of all believers. Men and women of every time and place have recourse to her motherly kindness and her virginal purity and grace, in all their needs and aspirations, their joys and sorrows, their moments of loneliness and their common endeavors. ... Mary, Virgin and Mother, shows us what love is and whence it draws its origin and its constantly renewed power." The Pope's carefully chosen words "Mary has truly become the Mother of all believers..." with its inclusion of the expression "all believers" (meant to include each one of us individually) introduces an intimate aspect of Marian devotion that can intensify and personalize one's relationship to Mary.

If Mary is mother to us all, it stands to reason that many of us will use a particularly beloved name for Our Mother, and indeed, it is part of our Catholic devotional patrimony to do so. Whereas Mary has many names and titles, and whereas many of us use many of these names and titles for her, the favored use of a particular name for her draws each of us individually into greater intimacy with her. The same is true for the various communities to which we belong. When any group, including a family, chooses a particular name or title for Our Lady, their use of that title draws them closer to Mary and to the mystery represented by the title in question. For example, if a family prays to the Madonna under the title of "Our Lady of Peace," the designation of that title presents an image of Mary who has a mission: the mission of peace. It's well known that many friendships (and even marriages) are formed because people became more intimately acquainted with each other by working together, by sharing a project; it becomes easier to relate to another if we share a mission with them. By calling upon Mary as Our Lady of Peace, it is reasonable to believe that not only will the believer find peace in his life through Our Lady's intercession, but that person will somehow become more intimately grounded in peace and become more of a peacemaker himself. One cannot pray to Our Lady of Peace without being reformed into a more ardent peacemaker himself or herself. Any title used in prayer for Mary draws one more intimately into the virtue or mystery represented by that title. Therefore, it behooves one to identify one's own favored title for Mary. Nations, religious communities, municipalities and families have been doing precisely that for centuries, and in doing so have been drawn into a closer relationship with Mary while simultaneously finding themselves drawn more deeply her work.

Here's the whole thing.