He was driving her crazy, Sam, slowly licking her fingers clean of the blood, his hand on her face, combined with the knowledge of what he was going to do, combined with the darkness in his eyes, all of it, he was going to be the one to break the last seal and she was going to be at his side when he did it, and then, then she'd make sure he got his rewards, everything he deserved.
"No one can Sam, no one"
Not even Dean, maybe especially not Dean, if she played her cards right anyway, and she knew the game better than most. Thats why Azazel had chosen her after all, she was the best, the most loyal, and she played the game of seduction better than any other. Not to mention seducing the younger Winchester wasn't exactly a hardship.
And then he kissed her, taking the last lingering traces of her blood and all Ruby could do was fall into it, that darkness in Sam, it got to her every time because she knew she herself had cultivated it in him, her and Lilith by taking his brother, and Azazel by...well, he'd built himself up quite the list.
"Staying?" she asked him, still perched on his lap.