1. Literal “burnt offerings” HAD TO BE male (Lev 22.18-19). Jephthah’s daughter obviously wasn’t.
2. Human sacrifice was STRICTLY forbidden (Dt. 12.31) and we have NO record of it being practiced (even in horrible Judges-period Israel) by mainstream Israel during this period.
3. The lament for the daughter is about ‘not marrying’ NOT about ‘not living’– it makes me wonder if some kind of religious celibacy is not in view. (Maybe the women at the Entrance to the Tent were celibate– Ex 38.8– living as widows in Israel later did on Temple payrolls.)
4. Verse 39 calls his action a ‘vow’. Lev 27.28 (coupled with 27.21) allowed people to be given over the Lord, who became servants of the Priests. As devoted to the Lord’s service, some of them probably did NOT marry (cf. the Nazarite vow, in its restriction on becoming ‘unclean’ for family members (Num 6.7) omits the words ‘husband’ or ‘wife’…perhaps it was sometimes involving celibacy. The only Nazarites we know, though, were married– Samuel and Samson)
5. As the only child, and if given to the priest in this fashion, Jephthah’s entire estate would go to someone else.
6. We have the VERY parallel case of Hannah and Samuel. She takes a vow, and offers her son to the Lord for all his life. (I Sam 1-2), and such vows did NOT allow the person to be redeemed with money (Lev 27.28-29).
7. Burnt offerings were ALWAYS associated with condemnation/evil– not thanksgiving and vows. Even the one non-literal use of it in Dt 13.16 (in which a town is offered as a burnt offering) involves abject judgment/condemnation– NOT at all in view in the Jephthah passage.
8. He would have had to offer her at some cultic site, which would have had a priest. I cannot imagine a priest (even those as lax as elsewhere in the book of Judges) that would have agreed to perform a human sacrifice!