By the time you’ve excused yourself to investigate the source of those moans, they’ve moved into his bedroom so she can straddle him and stretch again. You’ll work your way around the balcony, just in time to see her break on him. This is when you’ll realize that it’s not that she won’t stop fucking him. It’s that she can’t stop fucking him.
You’ll have your cock in your hand, matching his tempo without realizing it. Are you pretending you’re him, or just enjoying what he can do to her? You’ll bond for a moment when you’re both watching her face, to see how beautiful she looks as she breaks yet again.
The bond will snap when he sends long strands across her shoulder to her back and down her chest. You’ll lose count of how many times he releases on her because you’re cock is painting the concrete of the balcony.
She’ll return to the party, still bearing his marks under her little black dress. No attempt to remove them. She wants everyone present to know, even if it’s just subliminally, that she’s been marked by him.