What is the way to rectify the mistake of demanding separation from a girl with whom I have a romantic relationship, after her father, who is ill, learned of his illness?

Relationships between young men and women in the name of love are impermissible, whether with or without the knowledge of their families. If a man's heart becomes attached to a non-mahram woman, marriage is the solution, as the Prophet, peace and blessings be upon him, said: "We have not seen for two who love one another anything like marriage." If marriage is not possible, then they must turn away from this attachment, safeguard themselves through marriage, and repent to Allah for their negligence in such relationships. If you are able to marry this girl, then wait until her father recovers or Allah takes his soul, then propose to her guardian and hasten to marry her if she agrees. If she does not agree, then seek another righteous woman.