Unmarried
noun, の adjective
Not yet marriage? You haven't been married. You're unmarried.
みこん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
結局、未婚の女性ではないという真実を彼に話すはめになりました。
In the end I told him the truth that I’m not an unmarried woman.