In Portuguese this is used independently from Tatiana. In the 70s, 80s and 90s it was trendy to name girls Russian diminutives as given names - hence lots of Portuguese women in their 30s and 20s (often from poor backgrounds) are named Sónia, Tânia, Nádia, Cátia, and even Vânia (though Vanya is masculine in Russian!). No wonder most of these women are now naming their daughters classic, posh-sounding Portuguese names like Beatriz, Leonor or Matilde.