He was so close to being ready to accept what she had asked of him. Sam Winchester was teetering at that line, with words that weren't his but were Deans, and his fathers ringing in his ears. He didn't like what she had done, she could tell that, but he accepted it. And as he met her eyes and stepped forward to finish the job Ruby knew he was crossing that line with every step.
The demon died soon after, head torn from its body, blood streaming from its wounds, blood Sam didn't seem to be able to tear his eyes away from, that was alright too in her eyes. That was good.
She stepped forward again expression prideful, her hand running along his arm.
"Yes we are" she told him, allowing herself to relish in the scene just for another moment before turning them away from their victim, from that look of utter terror in his dead eyes. "Well done" she told him as they walked.