Considering that Professor Vulchanova founded Durmstrang, a school notoriously known not to accept Muggle-born students, it's possible that the Vulchanovs are an ancient pure-blood family. However, it is unknown whether this ban on Muggle-born students was enacted starting with Vulchanova, or during the two "dark periods" in Durmstrang history: the Headmastership of Harfang Munter or that of Igor Karkaroff, both after Vulchanova's time.