You were annoyed that Marlene had flirted with your brother. He was only a year younger, but you didn't want her having a relationship with him. During a break during class, you stuck it inside the broom closet and then went inside. You asked — almost like an order — for her to stay away from your brother. Her reaction left you confused. She laughed, as if you had told a joke and suddenly her voice became quieter

"And who said I want him?"

The message was very clear here. You could be a little slow sometimes... But she didn't really want your brother, she wanted you.