"her resemblance to the figure of Zipporah, Jethro's daughter"
In Exodus, Moses's wife Zipporah saves his life by circumcising their son, which Moses had incurred God's wrath by failing to do. The fresco of Moses and Zipporah in the Sistine Chapel is by Alessandro di Mariano di Vanni Filipepi, better known, as the narrator says, as Sandro Botticelli ('little barrel') (1445-1510).
Confusingly, there are two Zipporahs in the Sistine Chapel. The other is by Pietro Perugino (1446–1524).