What was her Chachmah?
Rashi (from Tosefta Terumos 7:20) #1: She told them, [if we do not hand him over,] he will be killed and we will be killed, give him to them. If he could be saved, e.g. he is inside and you are outside, and you are in danger and he Churban saved, we do not reject one soul due to another, i.e. kill him to save you. However, now that he will be killed with you, i.e. the walls will be destroyed and one cannot escape. It is better that he die, and you not die with him!
Rashi (citing R. Shimon, Tosefta Terumos 7:20): One who rebels against Malchus Beis David is Chayav Misah 1 .
Radak: Because the city was of Binyamin, she needed to entice them. The city is about to be captured. If we do not make Shlomo with them, Yo'av will consider all of us Mored b'Malchus, for which one is Chayav Misah! "Kol Ish Asher Yamreh Es Picha... Yumas" (Yehoshua 1:18), "Tenu ha'Anashim u'Nemisem" (Shmuel I, 11:12), just Sha'ul pardoned his honor, and did not kill them. Even though a king cannot pardon his honor, he commanded not to kill them. Also for [rebellion against] Divrei Chachamim one is liable - "Hen Lamus Hen Lishroshi Hen La'anah Nichsin v'Le'esurin" (Ezra 7:26).
Radak: Some versions say, this is only if he is Chayav Misah, like Sheva ben Bichri. Chazal said that they told Yehoyakim, Nebuchadnetzar wants you. He said, do we reject one soul due to another?! Will you kill him to save yourselves?! They said, so our fathers did to Sheva ben Bichri!
