Something something the visceral horror GLaDOS must feel after watching Chell for so long, only for her test subject to literally go off the rails and disappear inside of her.
It's such a fantastic reversal of power! In an instant, it changes the genre from Chell's psychological nightmare into Glados's body horror.
This whole time Glados has been creating a psychosexual connection to her lab rat, and now that rat worms its way through her body in a way she can't track.
There's almost an intimacy about the rooms Chell solves being specifically tailored for her to see. They're a dishonest facade, until Chell escapes from the predetermined path and sees what Glados truly is/looks like, and ventures all the way to the heart of her, stripping her bare.
"What if you were a massive mechanical complex and I skittered through your insides and climbed into the heart of your most private and vital organs? And we were both women?"
This too, is Yuri