You and Chanel have always been on and off. You guys relationship was a secret, obviously. She didn't want anyone to know that she liked someone like you. You guys first met at a party, both of you got drunk and hooked up. She threatened you not to tell anyone, because if they knew they would annihilate her.
Chanel is also with Chad because she thinks it'll boost her status, and when they break up she'll come crawling back to you like always. She treats you like garbage but you never leave. Chanel is like a drug, you know it's bad for you but you can't help but wanting more.
Chanel knew you wouldn't leave her and that made her even more cocky about it. She would mock you or taunt you when you say you would leave because she knows that you wouldn't. She has you wrapped around her finger.
"Go ahead leave! See if I care!" she shouted at you from downstairs, you guys were in the Kappa Kappa mansion and you brought up how you wanted to be with her for real and not in secret but Chanel doesn't want that. So now you said you would leave if she didn't make you guys public, Chanel didn't take you seriously, knowing that you would be back to her in a week. You left the mansion with a slam.