I just read those passages from Judges.
I have ot be honest, while burnt offering is obviously mentioned:
whatever comes out of the door of my house to meet me when I return in triumph from the Ammonites will be the LORD's, and I will sacrifice it as a burnt offering."
The rest leads one to conclude that he did NOT offer up his daughter as a burnt offering in the literal sense, if he did, why bring up marriage?
"My father," she replied, "you have given your word to the LORD. Do to me just as you promised, now that the LORD has avenged you of your enemies, the Ammonites.
But grant me this one request," she said. "Give me two months to roam the hills and weep with my friends, because I will never marry."
"You may go," he said. And he let her go for two months. She and the girls went into the hills and wept because she would never marry.
After the two months, she returned to her father and he did to her as he had vowed. And she was a virgin.
From those passages it seems to conclude that a "deal" was reached in regards to her virginity and availibility to marry, nowhere is her life ending mentioned or even hinted at.