Most interesting piece I've viewed in a while
I'm glad the game wasn't too long because I'm sure that music would get annoying in large doses. In fact I think the game format is actually a disguise, because imo this barely qualifies as a game, however I feel it's more like those rare breeds of interactive entertainment that has more in common with art.
The girl has some kind of deeper meaning but I couldn't pinpoint what to begin with until I saw all the endings which I'm sure was your intention, even with all the endings viewed it doesn't give too much away. This actually reminds me of a similar idea I had but never used, she could be many things like she represents a dull life routine.
SPOILERS DO NOT READ IF YOU HAVEN'T SEEN ALL ENDINGS
Its because of the hospital scene and her glitching however that it's clear it's him having dependence in escapism through some form of self destructive addiction, the girl is just whatever that addiction is in a physical form made up in his head to help him forget.
In lamens terms for people voting on this review his addiction to something has become so great he's imagining it as a person to help along with the addiction to forget about his problems. It could be drugs or alcohol or a bunch of other dangerous if overdosed stuff.
That's my theory at least but that's of course if I'm not totally barking up the wrong tree x.x hope I haven't made myself look like a fool