It is. They're two of the best lesbian actresses IMO. When they shoot a scene they're really into it and into the other woman. No faking, they make love as if there were no cam and never look at it.
I don't think they're lovers, they do mostly lesbian scenes cause they like women but in real life they're both into men. But I wouldn't say they give an imitation, cause they really enjoy what they do it's not just acting. I guess that's why they're always so good in their scenes.