What is the legal ruling in Islamic law for a person who repents and then returns to sin, after having promised a girl marriage and engaged with her in an illicit online relationship, and now wishes to separate from her and distance himself from these matters?

Satan is the enemy of man and gradually seeks to mislead him. Therefore, Allah Almighty warned against following his footsteps, saying: "O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins immorality and wrongdoing." It is obligatory to repent to Allah from speaking with girls and to cut off the relationship with her. It is permissible to marry her if she repents, but it is advisable to leave her and seek another righteous woman due to uncertainty about her repentance. There is no obligation to fulfill the promise of marriage to her.