The way they sequenced the story really turned the whole second half of this episode into being very focused on Hildegard. I think this is the first time we actually meet her and hear her talk in the show, and it is also when we learn about her backstory and relationship with Philia. Given her history with the Adenauers, it isn't surprising that she had stayed cold with Mia up to this point. I wouldn't be surprised if she had some kind of plan to escape Girtonia as it fell to monsters.
One of the things I like most about this story is how important the relationship between Mia and Philia is, despite them almost never interacting that we see. However, it's clear that they have managed to forge a strong bond in spite of the awful environment and people around them (or maybe because of it). I cannot wait for the revenge plot to play out.