Translation
This is the Posta di Donna la Sinestra (Lady’s Guard on the Left) and she is always ready to cover and wound. She makes great blows and breaks the thrusts and beats them to the ground. And enters the narrow play due to her skill in traversing. These plays such a guard knows how to do well.
Interpretation
Posta di Donna Sinestra mirrors Posta di Donna Destra. At first glance, they appear to be functionally identical, but there are subtle differences between the two.
One of the pulsativa (pulsing or beating) guards, from here you can make powerful cuts, using them to either directly attack your opponent or break the thrust. With the sword chambered so far around behind the body that is rests pointing forward, this generates tremendous momentum.
In particular, from Posta di Donna la Sinestra, by stepping through with the left foot, you can easily enter narrow play, using your left hand in front to pin or bind the opponent, while your right delivers attacks using the sword.