Same thing happened to me on two runs in a row, and I can't seem to get any other kind of ending. The most I managed to progress with Remie was getting her to say that she's rusty with people but was willing to try, then trying to interact with her just gives me her in her room fidgeting and a "what's she doing?" from the narrator. I spent like fifteen minutes managing rats and having Karina give me the silent treatment while I waited on Remie but no go.
The only CG I managed to find was getting buried immediately if you scream at Karina at the start, which I'm assuming is also what happens if the rats bite you to death or you piss Karina off too much in other ways?
Either way, I'd love an endings guide of some sort. I like the characters but I am very confused.