Did Jephthah sacrifice his daughter or just dedicate her to service at the Temple? No one knows. That's not the point of the story.

Don't make frivolous vows. If you vow something to God, it's His, whether you thought it through beforehand or not. Treat your words like a gun. Aim carefully. Know what's beyond your target. Don't point it at anyone unless you're willing to kill.
Judges 11:30-40