Meh.
I'm sure it's hard to be a cute girl and (apparently) being smart enough to graduate at the top of her class. I'm sure her parents are wealthy too, why not.
I don't think "introvert" applies here. Being an introvert means you don't feel the need to socialize with others - you don't get any "energy" from it, or rather, it drains you (For example, after a few days at the office, I'm completely spent and need to work from home, cuz I can't deal with everyone else's nonsense). The character in this story is just... shy? But her problem feels unearned. If she were a horrid obese pig, then sure, but she seems attractive with a normal figure.
I wonder if it's a translation thing.
EDIT: Right, I tried putting the original title in Google Translate: 陰キャ な 燕 和 変わりたい translates to "I want to change because I'm a negative person." Which is something COMPLETELY different from being an introvert.