Girl is right in that the world generally prioritizes those who fit the current beauty standards more, the main problem is that she redirected that anger towards her parents (who have no control over their own looks either, and on what physical appearance they end up passing on to their kids), and she got herself stuck in a social media bubble (which are often highly polished or faked, or even just outright scams) that continually wore down her self-esteem.
She may never achieve a "peace of mind" caused by a world that actually treats everyone fairly, regardless of their physical appearance, but she can still achieve a "peace of mind" where she no longer judges her own worth by how much she fits commercial beauty standards. She hasn't realized it yet, but confidence, living in the moment, and kindness are themselves a kind of beauty, even if it's not a beauty you can sell on social media.
(Like, visually, she looks so much worse in the panels where she sucks in her lips to avoid showing her teeth. She also tends to hunch down -- the things she does out of insecurity actively work against her.)
I'm also going to steal sensei's line: "Do you think that if you were like me, happiness would come to you?"
It's a good way to get someone (even yourself, if you're stuck in a similar doom/envy spiral) actually analyze and think about their situation, the things they say, and the world in general.
(Unfortunately backfired here: her obsession was already past the point of self-destruction. She won't realize what she has - a loving family who is patient towards her, a house, education, a healthy body, enough wealth to survive and spend on non-essentials, a school community that doesn't seem to be bullying her for her appearance - until she loses all of it, I think. Maybe if sensei pressed her about if her all her problems would go away if she achieved her desired beauty...)
And I think she showed by how she reacted to sensei that no, she still won't be happy if she was born pretty. She'll constantly stress about things that could "ruin" her beauty, and still limit herself from enjoying and being an active participant in her own life (like how she avoids smiling or talking, assumes cruel intentions from the people around her, blames people for what they can't control, and spends her money on treatments instead of on things she actually needs and enjoys).
