She expects manners.
She will probably be disappointed if you don’t open the door for her, or if you don’t pull the chair out for her at the restaurant.
Her family is your family.
Her dad will make fun of your weak handshake at first, and he’ll threaten you with his shotgun, but once you’re in, you’re in. Her sister will talk about what your future kids will look like, and her mother will be planning the wedding that you may or may not ever have. Also, her family is loud, and they are guaranteed to be in your business.