Rashi: People ceased living in Perazi cities (open, without a wall), due to the enemy.
2)
Why does it say "b'Yisrael Chadelu"?
1.
Malbim: When Yisrael entered the land, the Kena'ani ceased to live in open cities, due to fear of Yisrael. Now it is reversed, because the Kena'ani overpowered!
3)
Why does it say "sha'Kamti"?
1.
Rashi: It is like she'Kamti (that I rose). Also below (6:17), it says "sha'Atah
1
Medaber Imi."
Lev Yitzchak: Some texts say Bego Beis Yisrael. This is better according to Radak (4:5), who says that she does not prophesize for the future. Avos d'R. Nasan (34:7) says that Shali'ach (from which comes Ishtalcheis) is an expression of prophecy. Just like a prophet is called Av, a prophetess is called Em.
