You tell her that you still want to go out.

"Okay." you say. "I'd still like to go out. Do you think anyone will be able to tell that I'm wearing a diaper?"

"You've never been able to tell that I've been wearing one." Sarah reminds you.

"Yeah." you say. "But you usually wear dresses or skirts. Isn't the padding going to be more obvious under my trousers?"

"You're welcome to borrow one of my dresses." she says with a smile.