There are several more disturbing details of this story. The first being that Jephthah is pointedly described as being the son of a Harlot. This declaration is even more disturbing when the writer goes to great lengths to point out later, that after his daughter is sacrificed, Jephthah is not given any more off-spring by God.
The second is the custom of Israel which is said to be a four day a year lament for the daughter of Jephthah by all women... which I can find no record of ever being on a Hebrew calendar. It is probably there... but so far I haven't been able to find this period of lament for his daughter.
So this is one of the places in the bible that God asks for and gets the blood sacrifice of a child. There are others, which we don't like talking about either... we sort of brush over them like they were no big deal... but when our blinders are removed, they are exactly what they say they are.