What should I do about the refusal of the girl's family—the one with whom I committed zinā (fornication/adultery)—to allow me to marry her after my repentance, especially given that she intends to deceive whoever proposes to her?

Your duty is to repent and sever the emotional relationship with the girl. If the girl repents and you are able to marry her, that is good; otherwise, look for someone else. Restoring the hymen is forbidden. If the girl gets married, do not tell her husband about her fornication; rather, use allusive language. If he asks her about the loss of her hymen, she should deny that she committed fornication and tell him that the loss of the hymen has many causes other than fornication. Her family does not have the right to force her to marry someone she does not desire.