Judges 11:39

did with her according to his vow which he had vowed = He did not offer her as a burnt offering; for Jehovah could not accept th a t . Therefore Jephthah must have dedicated her to the LORD by a perpetual virginity. Such a vow was provided for in Leviticus 27:0 . See note on Judges 11:31 .

and she knew no man. This is conclusive. It has nothing to do with a sacrificial death, but it has to do with a dedicated life to Jehovah. Thus was Jephthah's vow fulfilled.

And it was = and it became.