1)
What is the meaning of "Lisgor"?
1.
Radak: It was about to be closed, for it became dark. Malbim
2)
Why did she need to say "b'Choshech"? (Surely the messengers know when they close the gate!)
1.
Malbim: They did not take a torch with them, for they fled.
3)
Why did she say "Tasigum"?
1.
Malbim: If you chase immediately, surely you will catch them. Therefore, do not be lazy from chasing and catching them!