Jack lowers his hands when Rose starts talking and making noises, wanting to see what goes on.
The ridiculous of her squeaking is funny, the teasing about the Doctor not being interested, but when Rose makes the remark about the dress... He flinches at that, not feeling any humor in it any more. He reaches a hand out to hold onto Rose's arm. "Hey, whoa, okay. Obviously Rose'll still be having a dress, and with you, just maybe let someone with a more objective eye do it or something-- but you really don't mean that, Rose."
He turns to start hurriedly pulling up the recordings, because he gets the feeling they need to clear this up in a hurry.