A theme that regularly comes up with her, even though she doesn't mention it that often, is that she thinks she's pretty. I won't argue that under the layers of lard, her features are regular; nothing wonky & had she been normal weight, she would have been reasonably attractive... nothing spectacular but she wouldn't have broken any mirrors either.
But due to her early onset & long standing obesity, that ship can't be said to have sailed, it never launched.
She could drop 400 lbs. at this point, have the best skin removal & plastic surgery available & would never be called pretty.
In any case, "pretty is as pretty does". Pretty isn't a personality type or character trait. It speaks volumes about her values or lack thereof, that she figures as long as she & others think she's "pretty", she's golden. Physical attractiveness might garner a second look from people who don't know you but if your personality sucks, in the end, it doesn't matter what you look like.
It can be annoying watching a vapid teen grow older & still try to ride the pretty bus while acting the snotty bitch but in her case, it's hilarious. I'd love to look into a mirror with he eyes, to see what she sees.