I can understand this at least, a lot of kids hit puberty and suddenly think that
1) they're mature enough to have sex with anyone they want and
2) they know everything there is to know about sex. I remember girls trying to brag that their
(totally real guiz!) boyfriend was in college, I remember sitting in 9th grade algebra and girls talking openly about how they would totes steal the 30-something math teacher right out from under his wife's nose, on the day he brought his infant daughter no less, and make
sooooo many babies lyke omgz.
What I'm getting at is yes it's wildly inappropriate but also not unexpected.
There's also kids wandering around the internet like Reinagoth who gets discussed quite a lot in the
Tearzah Hayes thread, who are groomed into thinking this kind of behavior is acceptable by predators like rottenginma who picked her up off the net when she was only 13.
Judging by this Mocha-Child's art style I'm going to hazard a guess and say she probably isn't any older than 16
(I checked her tumblr and she is 16, or younger if what @Stuckinatoaster says is true) so I can at least forgive her for being wildly misguided but it's better that other kids don't hang around her and have these toxic ideas rub off on them.