Child-coded vs. Adult-coded characters.
There are various ways to tell, but basically if you can increase or decrease the age of the character significantly and it will *not* seem strange, then they've probably been coded.
E.g. If they introduced MC as a 13 year old, that would be extremely weird. She might be petite, but she has an adult body, mental maturity, a career, and lots of bodily autonomy. So she's not child-coded because she does not look or act like a child.
YouTube has some really good breakdowns on identifying child-coded/adult-coded characters in anime, and there's lots of written research too! (sorry I'm a nerd about this kind of thing )
It's cool this is like actually super interesting so like nerd out dude
U know what I like?? The fact the drawings make her look like an adult. Idk but whenever I see a manga where it's like 'they treat me like a kid cuz I'm short' the personality is always childish or they draw them weirdly. Dunno how to explain it...