Amazing Girl seems like she'll be the type of person to be heroic yet antisocial. However, after stopping Evulz's plans, she sticks around to sign autographs and chat with people, and arrange counselling for Emperor Evulz's wife, children, and the minions who loved him.
Amazing Girl was a case of this trope but she realized that her personality issues were causing a lot of problems in her life. After all, just because she hasn't really done a Face-Heel Turn doesn't mean that what she is doing is okay, so she tries to stop her personality problems before things get worse.
Double Subverted: That was a one-time thing. Most of the time, she's as antisocial as they come.
It becomes clear that Amazing Girl is only acting this way to cultivate a "brooding loner" image.
Amazing Girl: I have done a good deed once! Therefore I can abuse people as much as I want!
Amazing Girl lives in a Crapsaccharine World where being nice, polite, friendly, and merciful is heinous, and being rude, angry, condescending, and violent is honorable.
Her attitude is dependent on her mood. If she's having a good day, she'll stop and chat with you as if you were old friends. If she's in a bad mood, she'll be antisocial.
Sometimes, Good Is Not Nice, but sometimes Good Is Nice.
Averted: Good is nice.
"Alright, we need this new hero to have a flaw. Let's make her a real jerk!"
The author wanted to make point about morality, being Cruel to Be Kind and Tough Love, & how being good doesn't entail being nice and vice-versa.
"I'm tired of nice, soft-hearted heroes. Let's prove that nice heroes finish last and mean heroes get the job done!"
The author wants to make a foil for the Affably Evil Emperor Evulz.
"Just because I'm the good person doesn't mean I'm a nice one."
"Amazing Girl isn't a nice person." "But she's still a good person."
Amazing Girl, when starting out, is nice to people and that puts them in harm's way. So...
After seeing how annoying a super hero's popularity is, she wears a jerkass fašade to avoid the unwanted attention.
Amazing Girl's mentor gives her a test to see whether or not she is qualified in being good by placing a To Be Lawful or Good dilemma; Will she spare an innocent who has caused destruction to society or will she send them to prison in order to save the world.