It'd be a deal breaker for me. It's highly possible your daughter thinks he'll change his mind, but he won't. The age difference itself between the two of them is not a big deal, but a 41-year-old has done many things and has already made up their mind the direction their life is going to go.
"Why would you ruin perfectly good peanuts by adding candy corn? That's like saying hey, I have these awesome nachos, guess I better add some dryer lint." - Nonny