Walk On
Hermione Granger died during her seventh year at Hogwart's. Along with a few other hundred wizards, Hermione fell in the fields of Hogwart's in the final days of the Battle against He-Who-Must-Not-Be-Named. Her death was mourned all over the wizarding world, a statue in her likeness was built in the exact spot where her body was found.
As for her spirit, Hermione chose to stay behind to keep Harry and Ron company. For the next few years after her death, she followed Ron from Romania to America where he found a quiet girl. The girl whose name was Joanne reminded her of herself. Ron came back to England much later to settle down with Joanne.
A week after the wedding Hermione left and stayed with Harry and Ginny, who was pregnant with her second child, James. Their first child Lily was three years old by then.
Hermione saw the Potters grow old; she saw Dumbledore and most of the Hogwart's faculty leave and die; she saw the world change. And when the last of her contemporaries passed on Hermione chose to walk on. She went to Hogwart's where she was most welcomed by the ghostly residents.
Since the year Hermione made Hogwart's her residence, it is said that Moaning Myrtle never moaned alone again.