Sasha

I've heard that Sasha means "guardian angel" in Russian.

Sasha is a Slavic name and although it is more commonly used for boys it's actually a unisex diminutive form of both Aleksandr and Aleksandra. See: Aleksandra "Sasha" Soldatova a Russian female gymnast. I've noticed that there are a remarkable amount of male footballers called Saša.

Its origins are NOT as a boy's name :) This is the nickname for Alexandra/er, and "Alexandra" was one of the epithets given to the Greek goddess Hera (goddess, not god!) and as such is usually taken to mean "one who comes to save warriors (men)". So originally this name was just an "occupation"... female occupation, btw. Also, the earliest attested form of the name is female. Sasha therefore is of female origin too.

Sasha is actually the diminutive in some form or another for the male Alexander and the female Alexandra. As most countries view it as only a diminutive, it is not a formal name. There are a few countries near the Black Sea that use it as a formal name or that language variant and it is unisex.

The meanings of the name Sasha:
1. From English — sunshine
2. From Japanese 幸 (sashi) — blessing, fortune, happiness
3. From Japanese 優しい (yasashii) — tender, graceful, affectionate
4. From Hindi शशी (shashi/sashi) - the Moon

Sasha is also pet form of Satyana.

Could also be a potential nickname for the feminine German name [Saskia].

I found a name meaning also to be "a helpful friend". I have only ever met one human being called Sasha where I live as the rest of the name bearers seem to be dogs. A very popular name to call a female pet dog.