Brief her first.

"Before we go in, I want to make sure you know your character."

"Alright, I'm playing your bimbo girlfriend. What else do I need to know?" She asks.

"Your name is Krysti and you're 21 years old. You refer to me as baby."

"Okay, what else?"

"You were a cheap whore before I met you."

"Okay..."

"And I decided to make you my girlfriend because you're really good at sucking dick."

"Is that..."

"All of this is completely necessary back story."

"Of course it is."

"You love it when I spank your ass, you giggle every time."

"Okay. Got it." She says seriously.