He didn't know he was hurting her. No, Sam thought he was being the perfect boyfriend, and he was. He was being amazing. He was saying that he loved her, moving across to her, treating her like a real live girl. But of course he didn't know the whole story, she'd kept it from him. She wasn't the 'good demon'. She wasn't 'different'. And if he knew that, he'd leave her. She couldn't tell him, she couldn't ever tell him. He'd leave her and Ruby couldn't have that.
She stood as he moved toward her, wrapping her arms around his waist and looking up at him. "I know you wouldn't be here. If I was just like the other demons. If I was the same. You'd leave me in a heartbeat, you'd walk away. You're not a moron. You're one of the smartest men I know. But we have this don't we. This romance if we're going to call it that. And its because of you I don't do that stuff anymore".
That part was true of course.
"Sam" she said softly, voice almost cracking as she spoke, "I need you, I need you to put aside those worries and be with me, now, here. Can you do that. Can you be the boyfriend I love. The one that changed me so completely I dont think that I know myself anymore." Ruby wasn't crying or anything but she was acting different to usual. He was with her in spite of what she was.