A/N I do not own Harry Potter and am not JK Rowling. I just like to play in her world for fun.
Her Final Day
One more day at Hogwarts, that's all she had left.
She hoped that she could come back but knew logically it was highly unlikely. As soon as she had seen Harry's face she knew it was time. It had taken 6 years of training and heartbreak but it was finally time. Time to do what she knew she'd have to since her 11-year-old self sent a scrawny Harry Potter to face a monster. She knew then that she'd never leave him again.
She's been planning for this day for years but always thought she'd finish Hogwarts before it happened. Now it had come she didn't want to leave. The magic of Hogwarts was so reassuring and warm that to be without it now would be like taking away a parent, that protection you get from being in the arms of someone who loves you unconditionally. This is where Hermione became Hermione Granger, where she learnt what friendship, bravery and strength were. Where she learnt what death and bigotry and rage felt like. This was her childhood, where she became part of a whole different world.
Harry saw her too, saw her for what she was just as she saw him for what he was. A scared child hoping that entering this new world would make life better. He might not know the details but she knows there are moments of understanding between them that Ron can't understand fully. Ron isn't ignorant, but he doesn't appreciate just how wonderful and scary and mind boggling this whole new world is. Even explaining exciting muggle inventions like the computer and the internet can't make Ron appreciate the differences.
But now even her last link to the normal world would be severed. Her parents would be happy she was leaving Hogwarts, it was the only thing that would help her obliviate them when it came down to it. There was a time for explanations and arguments but this was not it. Now was the time for tough choices and goodbyes and having faith that somehow they would survive.
Her dreams used to be becoming Head Girl and leaving school with top marks. Her boggart was her failing a test.
War changes priorities. Friendship changes priorities.
Now she dreams of surviving. Her boggart is them failing.