Go Go Power Couple

This, Miss, is really good quality artwork... but as a newbie in the realm of "The 100", I'm trying to straighten my understanding out regarding these two girls, who it *seems* might well be Clarke Griffin and Raven Reyes- whether those two are merely friends and co-workers, or if Raven is Clarke's adopted stepsister, or if Raven is in fact somehow Clarke's stepmom.
I don't care which arrangement those girls have, as of right now; all I want is to know *what* their relationship is. I'm trying to do research on that series, but I seem to have hit a wall- could you help me out, as a more knowledgeable fan of "The 100"? If you'd be so kind as to assist me with grasping the relationship that the series has, I'd be very grateful, in fact, I'll be grateful for any assistance you can kindly provide me in comprehending the relationships in the series.
Thank you in advance, and for this piece of fanart, it's very good quality work;
Sincerely one of your hopefully many fans;
Adalack.