I guessed as much, Shino hasn't processed her brother's death at all. She knows he's gone, but she doesn't want to properly grieve over it because it's too painful. Instead she's chosen to act as if she's already gone through the whole process of grieving, hoping that by faking it long enough it'll become real.
I feel that both Shino and Nozomi need to stop pretending they're fine, and instead sit down and grieve together. Until they properly face what the've lost, and come to terms with it, they'll never be able to move forward.
I'm fairly sure that's kinda on purpose. Shino and Nozomi are both struggling with grief over the death of a loved one so them struggling to move on and taking forever to do so is fairly accurate.
Also, as the series goes on, I'm becoming more and more paranoid colonel is her brother's reincarnated spirit/sent by her brother before he died, or some other nonsense that might come full circle.