Is NOBODY wrong in the post ? POST : 
I’m in need of some advice my best friend who I called my sister was staying at my house every weekend and when she comes over she hangs around my brother more than me she has even slept in his bed a few times, admitted to me she hooked up with him and gets angry when he mentions other girls around her so what I’m pretty much asking is am I the asshole for distancing myself from her, like was it a breach of “girl code” as me and my brother are close.
She had mentioned it before they hooked up and she definitely knew it made me uncomfortable and is becoming obsessive with my brother. 