Jace’s walking down the hall, headed towards his bedroom to change out of his blood soaked clothes - he and Clary just returned from Magnus’ in whose care they left Luke - when Isabelle steps in his way, smiling sweetly - which is never a good thing.
“Yes?” he says cautiously.
“Can I talk to you for a moment?” she asks, directing him quite firmly into the first available room off the hall.
The moment they enter the unused bedroom, Isabelle whirls around, her smile gone. She grabs Jace by the front of his jacket and slams him against the wall by the door.
“What…?” he wheezes in surprise.
She steps closer, her face now barely inches away from his, and hisses, her dark eyes blazing, “Don’t you ever, ever talk to my brother like that again!”
“Your brother?” Jace retorts, becoming angry himself. “What happened to our brother?”
“You lose your right to call him that when you stop treating him that way!” Izzy whispers furiously. “I like Clary, I really do, she’s a sweet girl, but the way you act around her? Like a dog with a bone, snapping even at people who are good to you!”
Jace glares at her. “He lost Clary…”
“She got herself lost when she didn’t listen, because that’s what she does, she simply does not listen. She has guts, I’ll give her that, but she has no discipline, she does not understand what she’s up against, not really. If you want to yell at someone, go directly to the source and stop venting your frustrations on Alec! Is that clear?” she demands. When Jace opens his mouth to protest, she pulls him away from the wall and slams him against it once more, almost rattling his teeth. “Is. That. Clear?”
“Yes!” Jace growls, eyes narrowed.
Isabelle lets go of him and smiles again, sugary sweet. “Good. I wish you goodnight, brother.”
And with that, she leaves.