What is the ruling concerning parents who shelter their daughter, an adulteress, who killed her illegitimate newborn, and has not shown repentance? And how can she be dealt with when living with her in the same household?

If what was mentioned about the girl is true, then she has committed abominable acts such as adultery and killing a soul, both of which are major sins. She must be advised to repent. If she intentionally killed the newborn after birth, she is liable for its blood money (diyah). If she aborted the fetus, she is liable for the fetus's blood money, which is one-tenth of the mother's blood money, and she inherits nothing from it. There is no blame on her parents for sheltering her. However, her guardian must be firm with her and take her to task, based on the Almighty's saying: (O you who have believed, protect yourselves and your families from a Fire), and based on the Prophet’s (peace be upon him) saying: "Each of you is a guardian, and each of you is responsible for his subjects." She should be reminded of Allah and instilled with fear, using wisdom and gentleness. If she does not repent, then boycotting her is permissible according to Islamic guidelines. Caution should be exercised with her as long as she persists in her state, based on the Prophet’s (peace be upon him) saying: "Do not accompany anyone but a believer, and let no one eat your food but a pious person."