I agree with your understanding. In support, consider the following discussion.
Some critics and scholars have condemned Jephthah for his vow, having the view that Jephthah followed the practice of other nations, offering up his daughter by fire as a human burnt offering. But this is not the case. It would be an insult to Jehovah, a disgusting thing in violation of his law, to make a literal human sacrifice. Read Deuteronomy 18:9-12. Jehovah would curse, not bless, such a person. The very ones Jephthah was fighting, the Ammonites, practiced human sacrifice to their god Molech.-Compare 2Kings 17:17; 21:6; 23:10; Jeremiah 7:31,　32; 19:5,　6.
When Jephthah said: “It must also occur that the one coming out, who comes out of the doors of my house to meet me…must also become Jehovah’s,” he had reference to a person and not an animal, since animals suitable for sacrifice were not likely kept in Israelite homes, to have free run there. Besides, the offering of an animal would not show extraordinary devotion to God. Jephthah knew that it might well be his daughter who would come out to meet him. It must be borne in mind that Jehovah’s spirit was on Jephthah at the time; this would prevent any rash vow on Jephthah’s part. How, then, would the person coming out to meet Jephthah to congratulate him on his victory “become Jehovah’s” and be offered up “as a burnt offering”?-Judges 11:31.
Persons could be devoted to Jehovah’s exclusive service in connection with the sanctuary. It was a right that parents could exercise. Samuel was one such person, promised to tabernacle service by a vow of his mother Hannah before his birth. This vow was approved by her husband Elkanah. As soon as Samuel was weaned, Hannah offered him at the sanctuary. Along with him, Hannah brought an animal sacrifice. (1Samuel 1:11, 22-28; 2:11) Samson was another child specially devoted to God’s service as a Nazirite.-Judges 13:2-5, 11-14; compare the father’s authority over a daughter as outlined in Numbers 30:3-other child. (Judges 11:34) Therefore no descendant of his would carry on his name and his inheritance in Israel. Jephthah’s daughter was his only hope for this. She wept, not over her death, but over her “virginity,” for it was the desire of every Israelite man and woman to have children and to keep the family name and inheritance alive. (Judges 11:37,　38) Barrenness was a calamity. But Jephthah’s daughter “never had relations with a man.” Had these words applied only to the time prior to the carrying out of the vow, they would have been superfluous, for she is specifically said to have been a virgin. That the statement has reference to the fulfilling of the vow is shown in that it follows the expression, “He carried out his vow that he had made toward her.” Actually, the record is pointing out that also after the vow was carried out she maintained her virginity.-Judges 11:39.
