It seems that Amy is someone who filters readers.
Its fucking weird, dude.
Ive read a bunch of comments about her being terrible and an unredemeable bitch in reddit, where I first learned about this series.
She is kind of a huge idiot, but it seems thats about her being way too over her head so she does dumb shit... She doesnt seem that bad, like even on the flashback she was trying to diffuse the situation with the gang beating the MC while acting as if she didnt care to save face. But things went wrong and the shock was enough that made her stop acting like that and hanging with delinquents.
A truly bad person, wouldnt have stopped.
And now she did all that dumb shit about the coffe and while she could have just crushed Shirone for real or blackmailed him into being her semi-slave... All she did was to ask him for coffe to "hummiliate" him. And that didnt work.
Now, it seems she even got some respect by Shirone because she saw he has a lot of magic potential and the guts/bravety to pull things off.