I think i have given Chantal too much credit by saying that she is stuck in high school. I am downgrading her to somewhere between elementary school and junior high. Your average high school student has travelled to other countries or at least understands that you need a passport to travel and the concept of currency conversion. You have to be a complete imbecile to not grasp the simple fact that if they took the Canadian money, they would have lost on the transaction as it is less valuable than the US dollar.
I think the most baffling thing is the way that she simultaneously expresses her ignorance and arrogance when reality clashes with her simplified imaginary version of it. The way she refuses to admit that maybe she should have educated herself and instead blames others for her own failings; is still shocking even after years of following her.
If I may put my pop-psychologist hat on for a moment (mine has a twirly propeller on top).
I've often mused about her stunted emotional and intellectual growth. It's there, and obvious to anyone paying enough attention. But at what age is she stunted? I've come to the conclusion that there seem to be three ages of stunting at play.
The first major stunting of her emotional and intellectual development seems to have happened around the age of three or four. When we haydurs call her an overgrown toddler, there's a reason. Her issues with impulse control, tantrums, abandonment, all-or-nothingisms, sharing, fascination with shit, and maybe even her eating itself seem almost infantile. Just my rando guess, but something traumatic may have happened to her around that age (which, IIRC, corresponds roughly with Grandma taking over full-time child raising duty? Just a guess)
The second mass stunting seems to have occurred during adolescence, at the cusp of sexual maturity. Her gross jokes, her fart humor, her confusion about sex, her love of drama, her need to be adored, her obsessiveness, her Mean Girls streak, her disrespect of adult propriety, her antisocial tendencies, her general social awkwardness, her lack of foresight and planning, and her bipolar mood shifts bespeak of a never-ending puberty that has never been resolved. I'd guess the traumatic experience here happened around the age of 14-15, maybe as early as 13, and it might have been something as simple as being rejected in high school for being a fat freak.
The final stunting seems to have occurred around the ages 18-20, and it is more of an intellectual stunting than an emotional one, but not exclusively so. She seems to have given up on education entirely during high school (from what we know of her, I would guess truancy and absenteeism were issues in high school and college) Chantal is educated enough that she can correctly apply present perfect verb tense (have eaten, have seen), which Amberlynn, the Slatons, and Amy can't do (have ate, have saw), which suggests a minimal intelligence the aforementioned fatties lack. However, she displays a fatal lack of curiosity about the world and life itself that ordinary young adults thrive on. Her displays of basic lack of knowledge concerning history, current events, culture, politics, or literally any subject under the sun suggests a stunting of intellectual development throughout high school. In addition, she displays one of the most abject lacks of critical thinking skills that I have ever seen in a person who is not at least mildly retardo. Like zero, zilch. Those are supposed to kick in during high school, but they never did for her. She can report facts (kinda, she's pretty poor at it really), but she can never provide insight.
So, at her most adult and mature of micro-moments, she is like an under-educated 20-year-old. Other times, she is like a gross and obnoxious 14-year-old, and many times she is a raging, tantrum-throwing 4-year-old. Depends on which emotional or intellectual characteristic we are considering.
I will now remove my propeller hat.