She's not married yet and a virgin. The various translations simply indicate no husband and/or virgin. Note however that she becomes pregnant before they are married. That is the future the angel is refering to and that is what Mary is answering to. Neither her, nor the angel is taling after marriage. Do you need the sciptural references for the angel's visit to Joseph and another reference to the fact she became unmarried and pregnant?
True, but the announcement in Luke 1 does not explain that. Mary had no reason to presume any other manner of conception but the natural conception of Joseph in the course of her marriage, based on Luke 1:26-34.