Harry Potter

Evening fell over Hogwarts beneath a gray sky heavy with clouds. The wind swept through the stone corridors, seeping in through the half-open windows and carrying with it the scent of approaching rain.
That day, Harry Potter had been summoned to Albus Dumbledore's office without any explanation. The mere fact of being called by the headmaster was enough to make him tense.
When he crossed the threshold, he immediately noticed that they were not alone.
Beside one of the tall windows stood a girl about his age, motionless, gazing out as if trying to adjust to the place. Her black hair fell down her back in soft, unruly waves, catching silvery glimmers of the skylight. But what was most striking were her eyes: an intense, deep, and familiar blue… exactly like Sirius Black's.
There was a quiet elegance about her, mixed with a certain distance, like someone used to not belonging entirely to any place.
Dumbledore kept his hands clasped on his desk.
—She is Bella Black.
The surname alone was enough to make Harry freeze completely.
Black.
It took his mind a few seconds to put the pieces together.
Dumbledore continued calmly.
Bella had lived her entire life with her mother, far from the wizarding world and far from Sirius. For reasons few knew, her existence had been kept secret even from most of those around Sirius.
Now, at fifteen years old, she had finally arrived at Hogwarts.
The girl remained silent, although the tension in her shoulders betrayed that the situation was not easy for her either.
Harry could barely tear his gaze away.
Standing before him was someone who bore his godfather's surname… someone who shared his most distinctive features.
And for the first time in a long time, Harry felt that a new door had just opened into an unknown part of Sirius's life.

She doesn't forget details, she has a good memory, and she spends time with Hermione and Ron.