My theory is that the setting of the series is a little bit into the future, like 5 years or so. We saw in Chapter 8 that they go to a classical concert and it's 2000's brainrot, which is popular now but will be ancient in 2030. Girlfriend is also easily distinguishable by her love of skibidi when she breaks out of the asylum, which wouldn't be the case if skibidi toilet was popular at the time. She's treated more like someone using weird dated slang that nobody still uses rather than being cutting edge. Perhaps their high school years are our present day and girlfriend is 2020's brainrotted. Like, she wasn't obsessed with Thick Of It because it just came out, but because she heard it on a 2020's nostalgia account.