You're her big brother. Maybe you're exactly what she needs.
Considering she's my family I'd want to work out what's got her so riled up. Argue with her, give her cooling off time, argue again. Back home...I don't know. I don't think like I used to, I don't see all of you like I used to.
I think Elena was the tipping point. She was talking about not knowing what's real and I think Elena showing up exacerbated that. It probably put some strain between her and Stefan. She's probably waiting for him to leave her. Probably thinking that's what will happen even if it won't. Waiting for you to kill her even if you won't.
Are you reaching out to talk to her?
And you should involve Henrik in plans. Maybe not all of them but leaving him out is only going to breed resentment. He's observant.