Luckily for
Dame Simonetta the puffball is an immature specimen. The flesh is spongy, like a dense loaf of white bread. Presumably as these puffballs eventually mature, the outer skin will become brown and leathery, the inside will darken and turn into powdery spores, and a "belly button" will appear on top.
She is able to withdraw her sword without incident.
Here is a cross-section of a firm-fleshed young puffball, in its edible stage:
And a mature specimen ejecting its spores:
[f=59]
Stern (
Strong Hero, MV 9′′, AC 3, HD 4, hp 20, FC 4 men/hero, SV F4, L)[/f]