I believe the lady, from what we can see, is as symmetric as any human. Slice down the middle (front-to-back, blade lined up vertically with the nose). Take away one half. Generate a mirror images of the other half. The person looks basically correct (ignoring minor inconsistencies - scars, different colored eyes, etc.) If the third breast was on one hip, or in place of one ear or something. that would be solidly asymmetric.
(Yes, I get what you mean, but a third breast located there is no more asymmetric than having a single penis)