She looks at you while she's seated at the kitchen table in your apartment and says in a lower tone of voice, "You know why I'm here, don't you?" She slinks out of her chair to sit in your lap facing you, wrapping her legs around your waist. You sheepishly mumble something about your girlfriend and push her away. She persists, tackling you onto the carpet. She laughs and tells you, "this is going to happen tonight." She runs her fingertips through your hair while she closes her eyes and caresses your lips with her own...
Or, while walking along the sidewalk on your date she stops and turns to face you. She smiles and pins you against a lamppost and groans, "Dammit, kiss me!"
Wrapping her legs around your waist seems to be the universal "screw me now" body language. I wonder if that's the same anywhere in the world, if when she puts down the chopsticks and the rice bowl on the bamboo mat and wraps her legs around you it's nookie-time.