What is the ruling on marrying a righteous, pious girl, knowing that her father works as a manager of a usurious bank, and how should one deal with her and her family if the marriage is concluded?

There is nothing to prevent marrying a righteous and religious woman, even if her father works as a manager in a usurious bank, due to the Prophet's (peace be upon him) saying: "A woman is married for four [reasons]... so seek the one who is religious, and you will be successful." This marriage may be a cause for the father's guidance and a rescue for the girl from marrying someone whose religious commitment is not pleasing.

As for dealing with the girl's family, there is nothing to prevent it. Whatever the girl's father offers in gifts, food, or drink is lawful for you and unlawful for him, because the salary of a bank employee is Haram due to its earning, not due to its essence. It is advisable to try to win over the father's heart with kind words and deeds, while clarifying the ruling on his work, which is forbidden by Islamic law.