Mary is igher than all the saints; the reason people call her Blessed Virgin has more to do with people being used to claling Her that. However, as I said, Mary is higher thanall the saints and even though She does have the title of Siant, we call Her Blessed Virgin not because we thnk She is les than the others but because She is higher than them: we give Her this other title to diffirentate Her from the title of Saint. I mean, Sh eis Queen of Siants, isn’t She?
Also, it is because we love to call Her the Blessed Virgin or the Blessed Mother. A child doesn’t call his mum ‘Mrs’ or ‘Mother’ but he calls her ‘mama’ so with Mary, instead of calling Her saint Mary, we call Her (sweet!) Blessed Virgin Mary.