A muggleborn getting her Hogwarts letter.
She gets all excited and reads up on the houses, secretly hoping for Ravenclaw.
The time comes for her to go and on the train, due to her sharp humour and friendly nature, she makes a couple of friends.
The Sorting comes quicker than expected, and once she has the Hat on her head, he lets her know that she is Slytherin.
The muggleborn is confused and disappointed, due to the stereotypes she had looked up before coming to Hogwarts.
Sad and lonely, she makes her way to her new common room.
However, once inside this group of people, she notices that the older Slytherins keep a watchful eye on the first years, silently hexing older Gryffindors who snigger as they walk by.
She researchs, getting funny looks from the Ravenclaws, and finds out about all the great witches and wizards who were in Slytherin.
Suddenly, her attitude snaps.
She embraces being a Slytherin, and uses their somewhat dark reputation to her advantage.
She can change herself to suit her surroundings.
She can hold her tongue in class, although she challenges her teachers respectfully, and is labelled as a Ravenclaw.
As she gets older, she becomes famous at pranking people, and is labelled as a Gryffindor.
She is overly protective and loyal to the Slytherin first years, and is labelled as a Hufflepuff.
But deep down, it all comes together and despite her safe nature, she is through and through a Slytherin.