>>2411147Seconding this. There are two things at work: that the fabric is somewhat thick and the way it holds up over her skin.
An almost flat chest (just smaller than hers) could compensate by making the fabric thicker and retaining the same look, but were it to continue to shrink it would no longer hold up in place at some point.
With a larger breast size the issue would be that the chest becomes too prominent. Meddling with the fabric thickness wouldn't be of any help. Be it leaving it as is or increasing the thickness, the breasts would be jutting out to the front; reducing the thickness would make it look like bodypaint. Both would look bad, or at least not as good. There's also the issue that the garment wouldn't cover the breast entirely, so that it would need to be made wider - starting to change the design already - or else they would behave as if clad in a bra instead of a dress: being held up against the body, instead of free underneath the dress.
