You must progress the story until the whole uni is open during the day, so after you break in at night. Then, she will be sitting in one of the corridors.
Glad to hear it. I tried to replicate it too but I wasn't successful.
The closed apartments doors are my "clever" way of managing random procedural generation with a still limited pool of rooms (more will be added later). Basically, the more you progress in the game, the less chance there's to have a closed room. It's a way to limit the number of available room at the start of the game so you don't immediately see all the rooms. You can see it as a representation of the rooms you've yet to see.
Thought I'd report a bug I've encountered: (I presume this is the cause, since I can consistently reproduce it, after finishing the Hospital/University - up to Brookside Glade) If you attempt to enter an apartment with this room unlocked (one of the ones that said "Restricted. Keep Out."), your game crashes.