Jepthah's daughter would have bewailed her coming death, not her virginity, if she was to be sacrificed. Rather, she bewailed the fact that she would have to live her whole life without husband and children, performing service to the Lord, presumably in some menial capacity at the tabernacle. Yet she was willing to do this, because of her father's vow and her gratitude to the Lord for delivering her people from the Ammonites.

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8