Thanks for your reply. From digging around, I found that there's a character in '
Eugene Onegin' by Pushkin called
Tatiana, who is nicknamed
Tanya. It's interesting that
Tanya became popular in the English-speaking world decades before
Tatiana gained any currency.
I believe
Sasha is unisex in Russian. It can be a nickname for
Aleksandr or
Aleksandra.
I have come across
Anya,
Anoushka,
Vanya (as a feminine name) and
Katya being used in Western European countries, with various spellings. For example
Anoushka as Anouchka in
France, and
Vanya as Vânia in Portugal, and
Katya as
Katja in Germany.