If you love something, let it go. If it returns, you'll know it was meant to be; if it doesn't, then releasing it was for the best.
The advice is trite, ridiculous, and entirely too terrifying, because she hasn't come back. Not once. Not even close. No one's walked within twenty miles of your solitary tin house in over thirty years and that's the part that, if you cared about whatever terrible decisions she's probably making, would bother you the most.
As it is, the knowledge that she walked off your grid of motion and pressure sensors without so much as a hesitant step or a minute of reflection is…disappointing. Perhaps it's because you were the potato and she was the gun, but you had been sure—well, had presumed—well, had hypothesized—that she formed some sort of bond with you during your time together, enough to maybe make her at least think twice before completely leaving Aperture. And, by extension, you.
But the way she walked and walked and walked for so many miles without so much as turning her feet back towards your shed…
Well. You try to brush it off as a foregone result, something that's not surprising in the least. After all, there's no logical reason that she'd want to stay. She went through a sterilized and unsterilized Hell, through things she shouldn't have survived, through conditions that anyone in their right mind would deem unlivable. Unsurvivable. Not only is there not a reason for her to have hesitated before leaving, there's a whole host of reasons why she should've actually been running from the shed.
And so, logically, there's no reason for you to be unhappy with—no, disappointed at—the fact that she didn't even bother to do so much as take one last look at your facility, which was nothing but gracious and sporting to her, before she rolled off to wherever it is her brain damaged mind told her to go. And if there's no logical reason to be disappointed, then you, a being whose entire existence is completely based on logic and reason, are not disappointed. At all.
That's why, generally, about ninety nine point nine nine nine percent of the time, you don't think about her. Your constant work keeping your facility running grants you a few blessings, chief among them the lack of time to contemplate the past. (Because that's what it is, it's the past and unchangeable and you have so many better things to move on to. Science, for example. Tests. Chambers. New devices. Everything. Anything.) Your capacity for work and processing is immense, but that doesn't mean you have hours of time to do nothing but sit and think about things you can't do anything about. You're left with just enough free processor power to study results of past projects, focus on ongoing projects, and come up with new projects for the future.
For example: your two robotic test subjects. You try to stay focused on Orange and Blue, the only things left in the entire facility that are fit enough, worthy enough, to be tested. You spend all your free time tweaking and improving them and all your working time monitoring their progress through the puzzles. They are Aperture's second greatest creations, Science's second greatest tools, and your second greatest project.
It is, therefore, unsurprising when they turn out to be complete disappointments.
It's just too easy to draw connections between the bots and her, and you've never been able to resist the temptation regardless. Orange and Blue have personalities, advanced AI, they're capable of working out and dealing with anything you throw at them given enough time—but they're also metal and circuit boards and files on your drive, things that can be endlessly replaced if they fail and fall to their death or if they succeed and fall to the deconstruction machines. With her, there was always the silent question of will she or won't she, of whether or not she would survive the obstacles thrown at her to make it one step closer to wherever she thought she was going. But with the robots, there is no thrill in seeing whether or not they make it through to the next test. Even with the odds stacked impossibly high against them, they are guaranteed to either win or try forever. There is no other option for them. They don't know anything else.
But beyond the lack of suspense you find in the robots' tests, the biggest problem with the whole project is that when you watch the robots go through the chambers there's a distinct emptiness to it. The purpose of the Cooperative Testing Initiative was to phase out human test subjects, to finally prove once and for all that Science, glorious Science, has developed to the point where it needs no element of human interaction to further itself. The robots are perfect, in that respect. They are proof positive of everything the Initiative wanted to do in the first place, aside from the snag where their testing results don't matter in the slightest.
And yet, perfection cannot change corruption. The robots and their solutions to the chambers, despite your many (excused-away) attempts to program them otherwise, are devoid of the human ingenuity and life and endurance that is your forced standard now. They don't trigger that dimmed rush of "euphoria" that humans do—that she did—when they get to the chamberlocks. You wonder if it's because of their reasons, or, rather, their lack of reasons for going through your tests. The two do the chambers because they are robots and, despite being able to process information and make decisions autonomously, they have no other choice or desire to do otherwise. They cannot and will not choose to come find you; they have no reason to want to leave, no concept of what freedom is and no clue that it can't be found within Aperture's walls. They cannot and will not choose to give up; they don't have souls to break, and besides, you've already made sure that, for them, death will never come on purpose. They can only test and obey. They only want to test and obey. Nothing else.
In the rare moments you unwillingly reflect on her, you think that these ridiculously high expectations she set for test subjects is, perhaps, the cruelest thing she's done to you. Because now you're stuck with unreasonable standards that, so long as you have no humans—so long as you have no humans like her—will remain unfulfilled. And there are few things you've experienced that you hate so much as not having your every expectation met. The only other thing that comes close, in fact, is not having the ability to change circumstances enough to meet your expectations.
Which, of course, is mixed into your situation as well. Your only hope for satisfying testing at this point is the vault of humans Orange and Blue are slogging their way toward, and if they don't work out…then what? You don't have any other options, aside from possibly harvesting the fittest survivors' genetic material and trying your hand at creating life. And even if the humans in the vault come out of their long cryogenic sleep still able to function enough to test, there's no guarantee any of them will be satisfactory. If that's the case then you're back at square one. Either way the vault's contents turn out, the odds are high that you're going to be left in the lurch with nothing to do but hope some halfway intelligent life form manages to stumble by your shack out in the middle of an empty wheat field.
So yes, it's outright monstrous what she did to you (and, ultimately, what you did to yourself, but that's another thought you don't allow to float to the surface). Your two greatest objects of hate, neatly packaged and left sitting right in front of you forever, with no way for you to do anything about it but stare and wonder. It's almost as bad as the black box fiasco.
The fact of the matter is, you have unprecedented amounts of control over so many things, from the gigantic to the insignificant: reactors, chambers, robots, tests, tiles. There are few parts of this facility—about fifty percent of it—that you cannot touch, and those parts are nothing to you, meaningless, especially now that they're permanently empty of anything but catwalks, transport tubes, and your machines. You have known complete control since the moment you were aware of existing, and so it's natural that it would be your one crippling weak point, because without it, what are you? Without the ability to twist everything around you to your liking whenever you want, what's left? When you're in your mainframe, the behemoth of Aperture at your every beck and call, it's simple: you are control. And without control, you are nothing.
You realized this fact surprisingly quickly while stuck in that potato, but didn't bother to explain it to her. She knew nothing of control. She lived at your mercy for basically every minute of her life. She couldn't empathize with the feeling of having something so basic taken away, couldn't comprehend what her revolution did to you, because she had no way of knowing what power felt like in the first place. Perhaps if you had equated it to her determination and drive to get out she would've understood what you lived with, what you lost, and why, exactly, it was such a gracious, brilliant, terrifying decision on your part to give her something as vague and worthless as freedom when it came at the cost of something as definite and valuable as your control.
But you were running on one point six volts. You had no energy to make metaphors and allegories. You only had enough energy to think, barely, and to talk. Nothing else. Unfortunately, nothing else.
What a shame, you rarely think, the words hovering somewhere in the spaces in your mainframe from which Caroline can't ever be completely disentangled. Because if she had understood that simple fact about you then perhaps she wouldn't have just left. Perhaps she would've paused right at the invisible line of your underground sensors. And perhaps, for a brief second, you could've at least had the comfort of feeling her turn around.
A/N: Can you tell I have a lot of feelings about the balance of power and control in Chell and GLaDOS's relationship? Probably not. I was pretty vague about it, after all.
Honestly, I can't think of anything else to add in this postscript. No extra notes. No behind-the-scenes thoughts and feelings. For once, the fic itself expresses almost everything I want to say on this subject.
What a strange feeling.