The Apostle Peter said, "Repent therefore and be converted, that your sins may be blotted out…" Acts 3:19. To repent and convert means to turn your life around and stop sinning. If a person is living in sin, that person has not yet fully repented. People should be ashamed of their sins and desire to live by God's righteous standards. Just as Jesus "loved righteousness and hated iniquity (sin)," we are to feel great grief and disgust over our sins. (Hebrews 1:9) We clean up our lives because we actually hate living in sin! It is only after true repentance and conversion that baptism becomes appropriate. Peter said, "Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit," Acts 2:38.
Repentance is always good for everyone. However, to become a Christian requires another step. Jesus said, "If any will follow me, let him deny himself, take up his cross and follow me," Matthew 16:24. When a repentant person chooses to sacrifice his will and his life in the service of God by following Jesus, that dear one may be baptized. Romans 12:1,2, "I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service. And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God."
Water baptism is the outward testimony of the inward relationship between that person and God. If a person is not obeying God's will, then his baptism is hypocritical. Specifically, the woman in your question is saying one thing but living in sin. She should not be baptized.
