The secrets of Rowan Khanna (Y6 spoilers)

Everything falls apart (Chapter 7)

Rowan could barely keep her eyes open, she was so tired.
Yesterday she had stayed up way to long, but it had been worth it. The party had been so magical, so perfect... so even being tired now, she didn't regret staying so long.
"We need to clean up the rest of the mess we made yesterday later..." Nonie yawned, while sipping her coffee. There were still tables and folding chairs outside, and she wasn't sure if they had gotten all the trash yesterday.
But before they could do that, they needed to go to class.

Chiara looked around the great hall. "Tonks still isn't here? Breakfast ends in fifteen minutes, she's going to miss it. And class starts soon, she'll be late!"
Penny, that was drinking some sort of potion that was supposed to be a magical hangover cure (everybody else was scared to try it, because it smelled really badly) said that she had expected Tonks to drag herself out of bed by now. Maybe someone should go fetch her, she suggested.
Rowan got up, saying that she would go. She needed to go back to the dorm anyway, because she forgot Barnaby Jr. She didn't want to leave him there all day, so she planned to take him to class with her. Barnaby had always done that too, nobody seemed to mind.
So she made her way back up to the Hufflepuff dorms, having no idea what was waiting for her there...

Tonks was staring at the piece of paper in her hand.
She couldn't believe what she was seeing. This... couldn't be. How was this possible? Rowan, she... how could she do this..?
Tonks was startled by the sound of the door opening.
"Oh, you are already dressed! You should come down, breakfast is almost over. If you are not feeling well, Penny has some kind of potion that helps... if you're brave enough to try it."
Rowan had come in, and was now casually talking while grabbing Barnaby Jr.
"How could she act so normal?" Tonks wondered, enraged. "How can she pretend to be our friend, while she is stabbing all of us in the back?!"
Tonks got up, staring at Rowan, with an angry glare.
Rowan looked at her. "Is... is something wrong..?" she asked, feeling really uneasy. Did she know something? But how should she know, her nightstand was locked!
She got her answer almost immediately.
Tonks shoved the paper in Rowan's face. "What the hell is this???!!"
And Rowan knew immediately, she had fucked up. Yesterday, she had thrown away the letter she was writing to R... why didn't she just burn it, she wondered.
"Tell me it isn't true!" Tonks yelled, pointing at the paper again. "Tell me that you're not the traitor!!"

Rowan wasn't sure what to say. Lying was not an option right now. Tonks knew, and she was angrier than she had ever been before.
"Answer me!!" Tonks yelled at her.
So Rowan just stuttered that she could explain.
Tonks crossed her arms. "What could you possibly say to make this better??!!"
Rowan tried to come up with something, anything to say. But her head was empty, her mind had gone completely blank in panic.
"I'm telling the others." Tonks said, turning to the door.
Something snapped in place in Rowan's head, and she got in front of Tonks. "No, I can explain- I never wanted to-"
Suddenly there was something that scared Rowan more than being found out. It was the genuine fear on Tonks' face, as she got in her way. She looked like she honestly believed she was a threat... Rowan froze, seeing that fear.

Tonks took that chance to dash past Rowan, and run out of the room.
Startled, Rowan sprinted after her. "Wait, please! Hear me out!"
But she didn't listen, and just bolted to the potion classroom.
Rowan couldn't keep up, Tonks was such a fast runner...

By the time Rowan arrived in the potion classroom, she was out of breath, panting.
"Rowan..." Nonie looked at her. "You can't be- You're the..." She held her head. "No..."
Barnaby was staring at her too. "It's all a big misunderstanding, right Rowan? Right?!"
Tonks shook her head, saying that it wasn't a misunderstanding. It was pretty fucking clear that she was working for R. There was a letter written to them in Rowan's handwriting, with her signature. There was no confusing that.
Merula raised her wand. "You're done for, Khanna! I have always had a bad feeling about you!"
Nonie looked at Rowan, tears forming in her eyes. "You were going to give me away? Just like that? You could have gotten me killed! I thought you were my friend! Why are you doing this??"
Barnaby pat her arm, telling her not to cry, he was still convinced that Rowan couldn't be a bad person, even though she herself had told him so.
Rowan was tearing up as well. "I never wanted- I didn't mean to-"
"BUT YOU DID!!" Tonks yelled, both her hair and face bright red. She couldn't believe Rowan's betrayal.