Do you trust in the girl's repentance and leave the key in her possession, or do you take the key from her father and inform your family about the matter, while concealing her identity and alluding to her father due to taking the key?

If a Muslim is not known for open sinfulness, then concealing their faults is an obligation and beloved in Islamic law, based on the Prophet's (peace and blessings be upon him) saying: "Whoever conceals a Muslim's faults, Allah will conceal his faults on the Day of Resurrection." However, if concealment leads to the perpetuation of evil, then one should not conceal it, and the evil must be removed. In this case, do not disclose her matter, but alert her father to monitor her, change the house lock, and do not give the new key to her father, justifying this by concern for the house's security.