Uh, Hentai? I guess you could draw that conclusion. But I don't really see it.
Something about vanity? It works, it fits, but it's not what I see.
My interpretation is that the woman, like the troll, is also a folk spirit/ creature of the woods. I believe the troll is slightly envious of the woman's majestic form, and has convinced himself (herself?) that the woman must be vain. In the troll's eyes, the woman could only be looking at her own reflection.
The truth is that the woman actually isn't looking at her reflection, but everything else. She's looking at the fish, the creatures all around her, and even the troll. These things make her feel one with the forest, since she's shaped like a humans. Humans can't coexist with nature like the troll and fish can, so in a way she envies them, but instead of responding negatively, she tries to revel in their ability to exist so senselessly with the forest. So the picture is actually just depicting the troll's view of the situation. who knows what he could learn if he actually chose to talk to her. Hmmm, That actually sounds like a good story, I might have to write that story... Oh my, did you just inspire me with your inspired work!?
As for the art itself, it's as any inspiration/homage should be. It borrows just enough from the source material to be recognizable, but is entirely in your own style. It draws the viewer in for very different reasons than the original.
Good job. I'll be watching for your future art.