How do you convince your friend to ask for a prenup?

How do you convince your friend to ask for a prenup?

“My friend and her now fiancé have only known each other for a couple months and got engaged on their one month anniversary. They’re in their mid 30s and she makes about twice what he does. I’m concerned, so I told her to ask for a prenup, but she can’t see anything going wrong.
How can I convince her that a prenup is a good idea?”