Dorit is the niece of the tour guide Jakob. She assists him by tracking down and retrieving tourists who leave the group.
Dorit is a highly skilled practicioner of the Israeli martial art of krav maga. When Bart runs away from the group, she uses it to great effect to pursue and subdue him. Bart is surprised (and impressed) that she doesn't fight like a girl, "or even like a Milhouse."
After Dorit finishes beating up Bart, she tells him that she's had plenty of practice dealing with "punk tourists" like him, and it counts as her military service.
Behind the Laughter/Note
In Israel, service in the Israel Defense Forces is mandatory for most citizens. The term is generally three years for men and two years for women, and service in the IDF reserves is often required after leaving regular service.