It is all true what was said about Natalia's name on the previous page. In Russia Natasha and Natalia is the same name. Natasha is a considered shorter and less official version simply and it can compress farther (Nata, Natka). Another example, Anna and Anja - same thing; Olga and Olja. Some times this "shorter" version of the name is really not any shorter but it is less official and does not appear in documents, paperwork, etc. So Natasha Poly simply tried to differentiate herself from Natalia V on a catwalk and it stuck.
Pretty much every name has one or two variations, including my own and I am Russian.