Sasha is universally applied to both males and females, although to be fair, in Russian, it's culturally much acceptable to call Alexander Sasha in any context whatsoever, whereas Sasha as–in female Alexandra is reserved for informal communication.

Disclaimer: I speak Russian.

Sasha is an informal version for both genders, I don’t think there is any difference.

Source: I am Russian

Second that. Was born in Russia as well

As someone who grew up in a former Russian territory that speaks no Russian, even I knew that.

Sasha is derived from Alexander via its dimunitive, but obsolete form - Aleksashka - shortned to Sashka, further simplified to Sasha as per established name format of Masha (Maria), Dasha (Daria), Pasha (Pavel, Paul), Glasha (Glafira), Natasha (Natalia), etc.

In Polish, Aleksandra (also female version) is shortened up to Ola, good luck with that ;)

Jeez, thanks. I know someone who goes by Ola and is Polish, so I suppose her name is actually Aleksandra?

Most probably yes. And if it's Aleksander (male name), he'd be called Olek.

I asked, and her name is indeed Aleksandra. :)