A Totally Different Kind of Metamorphosis
The first time Grete, Gregor's sister, appears in the story, we don't see her. Like the other family members, she's just a voice behind a wall, trying to get Gregor to open up his bedroom door. Unlike her parents, Grete begins to moan and weep as Gregor refuses to open his door.
As the story goes on, Grete grows from a whimpering doormat to an assertive young woman. She's no longer Gregor's flighty little sister who needs to be protected from the big, bad world—or the big, bad bug. She's the only one in the family who can face Gregor in his new body, the only one who seems to be able to read his needs and respond to them:
[His sister] came in on tiptoe, as if she were visiting someone seriously ill or perhaps even a stranger. (2.7)
Her new responsibilities increase her stature in the eyes of her parents... and herself, for that matter. The story suggests that all of her care may not be the most well-intentioned, but an outgrowth of the enthusiasm of a young girl who gets to star in her own fairytale:
Perhaps, however, the romantic enthusiasm of girls her age, which seeks to indulge itself at every opportunity, played a part, by tempting her to make Gregor's situation even more terrifying in order that she might do even more for him. (2.22)
And when things get rough—she has to work as a shopgirl by day, study at night—the fairytale is over. Gregor is no longer the Beast to her Beauty, but a tedious chore. When he ruins her violin concert, it's the last straw. She refuses to call him her brother, and insists that he has to be disposed of just like any old household pest.Grete Samsa Timeline