What is the ruling of Islamic law regarding a girl who loved a young man and he promised to marry her, then he left her, and now she wants to go to him and ask him to return? And what are the Sharia-compliant pieces of advice that can be offered to her?

The girl must fear Allah, repent to Him, cut off her relationship with this man, and avoid seeing him or hearing his voice. She should also persist in prayer, frequently remember Allah, and establish the Salah, for "Salah prevents indecency and evil, and the remembrance of Allah is greater." Remembrance is a fortress for a person against Satan. Ruqyah Shar'iyyah (Islamic incantation) is also recommended, while being extremely cautious of seeking help from sorcerers and charlatans.