Before Gregor's transformation, Grete is described by her parents as "a somewhat useless daughter.’’ While this may seem harsh, reflect on her actions before. She is a typical seventeen year old girl; she's lazy, and since she doesn't have to really do any work- she doesn't.
However, once Gregor's change occurs, she has to change too. She, though visiblly disgusted, is the one who takes care of Gregor, but she also gets a job as a sales clerk. The more work she does, the more she sees a purpose to her work. In fact, when her mom interceeds and cleans Gregor's room, she becomes very upset. It must be noted that she does not seem to look after Gregor out of love. She pleads with her parents that he must be sent away.
“He must be sent away,” cried the sister; “that is the only way. You just have to try to banish the thought that it's Gregor. The fact that we have believed this for so long is our true misfortune. How can it really be Gregor? If it were Gregor, he would have long recognized that it isn't possible for humans to live together with such a beast and would have gone away of his own free will. Then we would have had no brother, but would have lived our lives and honored his memory. But this animal persecutes us, drives away the tenants, and evidently will occupy the entire apartment and let us spend the night in the alleyway.
Once Gregor changes, Grete steps up and grows up (she blooms in to the young lady). She is the one who alerts the famly that Gregor has died. In a callous manner she announces "“Everybody check it out, it croaked; there it lies, it's a stiff!" And with that, the now happy Samsas family leaves the house and lives a happy life.