Depression and inertia are the subject, but the story feels inert and one-dimensional to its detriment. It's not bad though. I like the idea that people will do whatever they can to give themselves a sliver of hope, even if those actions are hurtful and the hope illusory.
Fwiw, I'm not bothered by her treatment of the teacher and her boyfriend. Neither really matters in the story, and the former is a complete scumbag. Not that anyone here is innocent.