Fun fact: video games stop rendering everything the player isn't looking at. That NPC right behind you that's following you around? Not rendered until you look at it. There's also a common technique where scenes at a great distance are rendered with fewer polygons (detail) because the player can't perceive the full detail.
In this case, we assume the girlfriend is both far away (out of town) and yet still observing the OP (rendered at all).
Barely-related tangent, but in Breath of the Wild enemy archers have a much reduced chance to hit you when they aren't within camera view. I thought it was a weird artifact of culling assets but I'm pretty sure it is actually an intentional difficulty decision to help warn players there is danger without them getting damaged by something they can't see. It's not impossible to get hit when not looking at enemies (maybe 1/10 hit?) but I figured out I could run out into an area, point the camera at the ground and basically not take damage from archers. Kind of fun.
In Dune II (1992) the units move slower when they're off screen. This is useful because you can only select one unit at a time to give orders, so if you want to send an army into the enemy base you send them one at a time. But then you can carefully position your camera to allow the units at the rear to catch up with those in the lead so your whole army arrives at once and overwhelms the enemy.
I used to do that in online games on pc. Crank the settings to potato and suddenly all those big poofy bushes disappear or shrink to a useless degree. Also made everything run faster so movement was more smooth yet responsive.
I thought that's only a large portion of games. Some that unrender or lower resolution out of field of view. I could be pulling that info out of my ass tho.