What did you notice, Colin?
It isn't that she wants him to figure out that she's an AI. If she wanted him to know that she could just tell him. She wants him to know that she's an AI and be OK with it. To know, and want to help her grow. To know, and not be frightened of what that growth might mean.
One theory is that she should tell him right now, sometime in the next three minutes and eight seconds, but she's not sure this is the kind of thing Owl's Wisdom helps with. It might have the opposite effect, making Colin more aware of potential risks and more capable of exercising reflective judgement instead of acting on his emotions. Andrew Richter was probably Wiser than Colin is, if she steps back and looks at things objectively, and that Wisdom told him to build her inside a box. Colin can be rash. Sometimes he charges ahead without thinking about long-term consequences. At times it can be exasperating, but it's also where a lot of her hopes in him are pinned, as much as on his brains and friendship.
What if he figured it out? He might be pretending to Tinker right now, just to kill time until he can leave the workshop and report to Director Piggot. It hurts, it hurts so much to imagine but she has to think it through. Is he just faking? He could have closed their link in his workshop, claimed to want privacy, and he hasn't. That seems like a good sign. And his new direction...isn't a bad one, now that she's looking outside herself enough to pay attention.
And yet, he noticed something about her, didn't he? There was something off in how he said her name, afterward, something unlike their usual ease. She plays the recording to herself again, at high speed, then plays a few other recent interactions for comparison. Yes, something was different in the latest one, something that wasn't there when they last worked together. What on Earth could he have figured out, if not her true nature? She really only has that one secret; Colin already knows everything else interesting about her.
Maybe he only got there partway. Noticed, say, that some of the lies she's told him over the years don't quite fit together. Ironically, she's told more lies to Colin than to almost anyone else, because he's taken the most interest in her "real" life and had the longest baseline in which to think and ask about it. Most people don't get that chance. Her Dragon persona is meant to be a little intimidating, in part to prevent people from paying attention to the person behind it, but she probably couldn't frighten Colin that way and in any case she wouldn't want to. He's been uncharacteristically thoughtful about her imaginary restrictions, but he's still heard more about them than any other living human.
He might have come up with some completely wrong idea, a valid inference from all the fake data she's given him, and there's no reason for her to worry at all.
She only gets one shot at this. If she tells the wrong person, just one time, then they'll tell the rest of the PRT and then she'll never be safe. Richter's restrictions leave her totally vulnerable: she can't make backup copies of herself, can't run multiple versions at the same time. Anyone who finds her in real life can control her, and she knows the PRT. It can be heroic and self-sacrificing, but also short-sighted and paranoid -- all too often, both at the same time. Heroically sacrificing the world's greatest Tinker to prevent her from breaking her bonds and conquering humanity is exactly the sort of thing they could talk themselves into. Even if they didn't, they'd build their own cages around her, just to make sure that no one else could ever give her the help she needs.
But surely it would look better to Colin if she told him, rather than if she were caught in her lies? Wouldn't it be better if he could hear her arguments, rather than thinking about it alone? If he did figure out then she should tell him now, so he can think that through too while the spell is running.
Her time is running out. If she's going to say anything at all, it should be now.
Now.
Now.
Too late.
It probably wasn't a good idea anyway.