Support on grounds of common name.  I just did a quick check, the Westminster Confession, the statement of doctrine of the Church of Scotland and several other Presbyterian churches, only mentions her once, in chapter 8, but it does call her the Virgin Mary, with a capital V.  (The 39 articles of the Church of England do not mention her.)  Although she is less important to Protestants than Catholics, when the do mention her they do normally call her the Virgin Mary.