Is she Russian, or of Slavic origin?

If you look at her Instagram profile, you'll see that she speaks Russian, so I'd guess she's either from Russia or any other country that used to be in the Soviet Union.
I can't remember now, but I think she had a little accent on Shameless when she spoke Russian, so I'd say she hasn't had lots of practice.

She is American and has a perfect American accent. She was born and raised in Long Beach, California. Her Russian accent on Shameless is just acting.

She was born in Russia but raised in Cali at an early age. Her accent on the show is decent and her Russian is fluent. She doesn't have an accent in real life.

Her Russian on Shameless actually sounds like she's fluent in Russian. A lot of times in TV or movies, the actors playing Russians sound absolutely horrible when trying to speak Russian. She is definitely fluent which leads me to believe she's Russian or part.

She sure looks Russian they did a good job with casting

She was born in the USA but her parents were immigrants from the Soviet Union.

Goreshter sounds Georgian