They just prompted it to talk the way a 13 year old girl texts.
(Also they prompted it to pretend not to know anything about anything.)
If you used a smaller corpus, followed a different kind of fine tuning routine with rather normal conversation patterns, and wrote a different base prompt, I don’t see why it shouldn’t be possible to come up with a very particular personality, so to speak.
IIRC, PARRY https://simulation-and-society.org/parry/ got there in 1972 by pretending to be a paranoid schizophrenic person
PARRY is my spirit animal.
> In empirical evaluations conducted during the 1970s, experienced psychiatrists proved unable to reliably distinguish PARRY's responses from those of actual patients diagnosed with paranoid disorders, achieving only 48 percent accuracy, a figure statistically indistinguishable from random guessing.
https://www.cs.cmu.edu/afs/cs/project/ai-repository/ai/areas...