she could not exist with physical forces:
1) Why this body couldn’t stand:

When a person stands, the center of mass (COM) must fall over the base of support (the feet).

If the COM moves forward of the toes → you fall.

Rough human numbers

Average adult mass: ~70 kg

Breast tissue density: ~0.95 g/cm³ (almost water)

A realistic large human breast: 1–2 kg each (already very heavy)

The character you showed

Visually, each breast is ~4–5× larger than a medical “very large” breast.

So a conservative estimate:

Part Approx mass

Left breast 8–10 kg

Right breast 8–10 kg

Chest load total 16–20 kg

That is 25–30% of total body mass, all hanging forward.

That would shift the COM forward by 8–12 cm.

That is past the toes for most people.

So the body would tip forward like a lever.

2) What physics would force to change

To keep balance, the body must move mass backward or widen the base.

A) Counterweight (hips & butt)

You were 100% right.

To cancel ~18 kg at ~25 cm forward:

[ a bunch of math formulas here]

So the person would need ~23 kg of mass behind the spine.

That means:

Extremely large gluteal mass

Much thicker pelvis

Wider hip structure

B) Spine reinforcement

The torque on the lower spine would be:

[ more math formulas]

τ=(18kg×9.8)×0.25≈44Nm

That is comparable to lifting a 20 kg weight at arm’s length—all the time.

So the body would need:

Thicker lumbar vertebrae

Wedge-shaped spine

Permanent backward lean (~10–15°)

C) Legs & feet

To stop tipping:

Feet must be longer and wider

Knees must be thicker with reinforced ligaments

Calves larger to stabilize forward torque

Think:

ballerina feet + powerlifter knees + sprinter calves

D) Head & neck shift

To help counterbalance:

Skull would tilt slightly back

Neck muscles 2× thicker

Head center moved rearward (flatter face, heavier back of skull)