What is the ruling regarding a girl marrying a young man without her father's consent, in the event that the father refuses to marry her to a religious young man for non-religious reasons, knowing that there was a previous relationship between the girl and the young man? And how should she supplicate to God to achieve her desire?

You must realize that your emotions are exaggerated due to continuous communication with the young man, which is a mistake and does not align with the religion and morals you attributed to him. Furthermore, your father's refusal is logical due to the political circumstances in the young man's country, which could scatter the family, and the difference in nationalities, which causes many problems, as well as his desire for your well-being and comfort. You are not permitted to marry except with the consent of your guardian, who thinks with reason and wisdom, whereas you are thinking with your emotions. His refusal might be good for you, as Allah Almighty says: "And perhaps you dislike a thing and it is good for you."