Yes Ruby knew him, she had known of him from before he was born but it was only the last two years, the time when she'd found him, nurtured him, been so much to him, family when he had none, caring for him and nurturing him better than John and Mary Winchester ever had, being the little fallen angel on his shoulder. Being everything he needed, She knew Sam so completely.
And she knew that he was letting go, teeth at her neck almost piercing her skin, the blood he so craved pumping in the veins beneath his teeth, "You marking me" she told him gasping through the sentance barely even to speak anymore she'd leave it until it healed itself, she would be proud of it. Once his face buried in her neck, eyelids fluterring against her Ruby opened her eyes looking up at the ceiling, feeling the strength of each thrust as she aided him as much as she could guiding his touches, squeezing her thighs slightly closer to press against him
Moaning his name, and gasping occasionally about just how special he was before words failed her and she was overcome, screaming with a wild abandon that she rarely showed the world, she was not in control right now, not at all, And in spite of herself it felt amazing.
Ruby urged Sam on, giving up the last vestiges of calm and was lost to anything but Sam.