It was in the 57th minute that Sembrant nodded in 1-0 to the home team after a corner from midfielder Valentina Cernoia.
The goal was the Swede's first for the season.
A moment later, Arianna Caruso increased to 2-0 and after two goals in the final minutes, it finally became 4-0.
In addition to the full hit, Sembrant was warned with just over a quarter left.
Juventus leads Serie A with seven wins in as many matches and an impressive goal difference of 21-3.
Second-placed Milan are three points behind and have only lost one match.