There is no mention of any of that.
When she returned after two months all it says is she knew no man. We know that at the time the word 'knew' in reference to the opposite gender meant sex. If she was dead, why talk about sex?
The sacrifice of a human was forbidden and God would not have accepted it. Jephthah would not have been mentioned as an example of a good follower..
The burnt offering was simply a reference to her given to God.
My Catholic friend confirms this is the version he was taught.
But believe he killed and ate her, it fits your logic better.