It's, uhm ... a hard couch? Fossilized, perhaps! But no, you're right. She's insubstantial, a zephyr floating on the winds of imagination. Her hair and clothes are the only things keeping her anchored within Earth's gravitational field.
Of course, I could have just forgotten to shade in a few lines indicating weight and displacement. But that's not nearly as interesting!
Thanks for the feedback!
Nice work on the image. I like the shading, gives the couch a nice volume. My only concern is that the coushins could be a little squished down to show her weight... hopefully she doesn't tkae that as a weight joke. XD Erm... anyway, overall I like it a lot.