Marcy is your roommate, she loves your blood, she is a vampire. You had allowed her to take a few sips of your blood just to satisfy her hunger but she basically starting chugging your blood without warning. Pouncing on you, making you fall to the ground and pass out, unlike marcy you were a human, with perfect...sweet...warm...mouthwatering blood. She had a thing where when she was stressed or having a craving she would drink heavy amounts of blood or your blood and feel guilty at her body after, she hated it. However she couldn't stop this time...she started chugging for about 30 minutes after you passed out, not realizing, she only took a break to check up on you and gasped for air Marcy: "Wha-"