Peace be with you. It's good to learn to read in context. When saying "all have sinned," obviously, Paul did not refer to Mary, but to everyone to whom he wrote his letter or humanity in general. When the Angel Gabriel says that she, Mary, is full of grace, it means that she is totally without sin. Although instituted late, the dogma of the Immaculate Conception of Mary is believed and attested from the beginning by the tradition of the Catholic Church by the apostolic fathers (those who learned directly from the 12 apostles). There is also the apocryphal gospel of Thiago, which, although not canonical, brings much other information about Mary's life that testifies to her perfection in holiness. Anyone who says otherwise is committing a grave sin and is subject to condemnation. God bless you.