Girlfriend's dad told me this but idk what should i do?

Wait, and if he doesn't say anything, then leave it. It was hopefully just the alcohol talking. But if he does bring it up, and ask you if you got the number, try talk to him, and like you said, convince him that his wife is beautiful because the last thing you want is to tell your girlfriend or her mother, and then the parents may fall out, divorce and you know what I mean. Hope things work out.