Here's a study for people who actually have or have seen breasts in their life.
Examine this picture:
http://g.e-hentai.org/s/022b935e0f57...4-jpg/178841-3
Look at the curvature of the cleavage. How the breasts are shaped, and how they're resting.
She might have a future career as a prop designer for MistressTaylor, at least.