Ultimate shoulder rides

I was recently over by my sons house for a backyard party. One of the girls 20 yrs old dressed in shorts jumped on her boyfriends shoulders while he was picking up a dropped wallet. She aggressively sat on him before he could even stand up she had her feet locked behind him and kept yelling "Lift me you coward". I,ve never seen such aggressiveness in a woman before.After he stood up she was slapping him in the head. Come on move. It almost looked rehearsed. But the look on her face looked like she has been trying to do this for a long time and finally got the chance. And he looked like he had better do it or there would be more trouble.   Have any of you felt like this? Is it a power thing over the guys? Or is it a sexual thing? Can any of you answer this for me?