Hey Brit, thank you for your interest!
Well, the wings are real, although sized down on Photoshop because they were too big for what I wanted. The feet are real, although also photoshoped to be smaller and in a different pose. The body shape I believe it’s real too although a bit more exaggerated in photoshop too, I need to check. I think it’s nude clothing, top and bottoms because they aren’t compatible with the harpy feet, I had to take separate shots to edit it in. The tails, unfortunately, are drawn in. I just couldn't find any that looked good since there aren’t many to choose from anyway. I’ll link you to the stuff I used.
DEMON WINGS: It says it’s only for male, but you can tweak it in simPE so females can use them too as an accessory, here is the trick: http://modthesims.info/t/396108. There’s some other wings too down on the chunky tails link lol
BODY MESH: It was indeed nude separate top and bottoms, from Warlokk’s Hi-Res nude bodyshape. The link will take you to SexySims, it needs login, if you don’t want to, I can send it to you.
HARPY FEET: Made by SynapticSims, he has an account here on tumblr too. Give a browse to his site, he has werewolf feet too (Thea’s first draft had werewolf feet actually), among other body modifications.
For tails, there isn’t much you can find, SynapticSims has nightcrawler’s tail. You also have reptilian tail, forked tail, gorgon half-body, these chunky tails, and fox tails.
EDIT: Extra wings and tail.
The rest, I had to recolor it all, I edited all the skins and recolored the wings and the harpy feet. Hope it helps!