I am also curious what exactly she found on FB. I don’t think it’s great behavior to call someone at 5:30 a.m. to confront them about their potential lying over something you saw on social media, even if that something turns out to be not much. FB isn’t real life. Also? It seems pretty clear that she doesn’t trust you from that interaction alone, LW. If it was something recently uploaded, there are ways to bring it up without waking someone up to flip out at them.
Anyway, FB was really new when I was in college. I did know couples who fought over things that one saw on FB. I even once had a bf who would get jealous if another guy wrote on my wall (lol). I assumed you’d be early 20s or younger with this level of drama, LW.