Shall I compare her to 'real' characters?

Mary Sue is more precious and perfect.

All the boys at Hogwarts desire her:

Helpless against the allure she projects.

Often her hair is as the raven's wing,

Glossy black with ruby glimmers it shines.

Other times she's a blond angel that sings:

With a voice, like her figure, so divine.

The transfer student with latent powers,

Who masters complex magic from the start,

Always saves the day smelling like flowers:

Defeats Voldemort or dies winning hearts.

A dream of a girl too good to be true;

Sugar coated poison is Mary Sue.