Idk it might sound too much but you should inform the local police about it or just casually ask them what can be done in such a scenario. Because it’s good to keep them in loop if the things go south. Another thing, your father have that call recording of saying no to the girl’s father? If yes, then good. If no then get that recording somehow. Make your father call them again and politely saying no and requesting the girl’s father to understand his point.
All these things might be really helpful.