Regarding Judges 11:30-40, It doesn't explicitly say that Jephthah killed his daughter. Jephthah carried out his vow by dedicating his daughter to a life of perpetual virginity, that was the sacrifice. Human sacrifice was contrary to the Law of Moses and God would never accept it (Leviticus 18:21 & 20:2-5). Whatever or whoever came out of Jephthah's door would be offered to God, an animal would be a burnt offering and a human would be dedicated to the Lord. The indication that the daughter went into the mountains to bewailed her virginity for 2 months and knew no man supports celibacy.
"Then she said to her father, Let this thing be done for me: let me alone for two months, that I may go and wander on the mountains and bewail my virginity, my friends and I" (Judges 11:37) She was sad over the fact that she would never marry, not that she was going to die.
"She returned unto her father, who did with her according to his vow which he had vowed: and she knew no man" (Judges 11:39). What was the result of her father doing his vow? "she knew no man".
Paul mentions Jephthah in Hebrews 11:32 along with other faithful people like David, Sampson, Gideon, and Samuel. So Jephthah was not admonished for his vow, but it appears to have been a righteous vow. “She was his only child. Besides her he had neither son nor daughter” (11:34). For his daughter to be consigned to perpetual celibacy meant the extinction of Jephthah’s family line, so in that sense, it was quite a sacrifice.
