Glad you liked it, Melvelet! Going in blind is probably the best way to view this one actually. I knew beforehand that it was a horror, and a slow burn at that so I was more prepared.
(Incidentally if you haven't seen 13 Tzameti
that's another that excellent going in blind. Completely diff type of film though)
One other thing I didn't mention before has to do with the transition (the last 20 minutes you refer to)-
right after the deed is done and Simone, still naked of course, leans over his body and turns the light off when she hears people approaching. In the lower light, with her back to the camera the viewer sees her more as a "creature" and possibly inhuman in some ways; her back and spine almost contort as she reaches over his body and give an almost inhuman appearance in the lower lighting. It's a creepy visual during the transition from her "innocent state" into something more sinister
Aside from that there are items in certain shots that probably have meaning, but are not the main focus of the shot: e.g. paintings on the wall that Simone examines when they first get to the flat. I'll rewatch this again at some point and check those more closely.
The other scenes I mentioned:
first one is the lipstick on the mail carrier
I have to think that this indicates that Simone's mail carrier is having an affair with her mother
. This is the scene when she leaves class and runs home to check the mail (at a time of day she normally would not) and they confront each other. Nothing is said, but I think this might be significant somehow. Based on the opening scene the mail carrier (and other postal workers) seem a mused and unsympathetic to Simone and are, for her, the nemesis. They get worked into the paranoia pretty easily and are obvious targets for some of the delusion.
The nightmare/dream in the car might just be an extension of Simone's fantasy state. There is obvious angst mixed in with the fantasy and this might just be a more surreal visual tied to that. Not sure if the pink flashing lights mean anything there...
I'm going to rewatch a couple of these scenes before I post more (also I am at work taking a break and have a meeting now). Lost of subtlety with meaning in this film. It begs me to watch again.