Hermione had always known, deep down, that she was a Gryffindor.
When she rammed the Sorting Hat onto her head, the movement had been fuelled less by eagerness and more by nerves. A sharp mind, the Hat had said, a thirst to be taught, for knowledge. A Ravenclaw, surely, but… By this point, Hermione had stopped breathing in anticipation. Bravery, and unwavering loyalty. Put your mind to it, girl, and you'll go far. GRYFFINDOR!
A resounding cheer, and she was off, down to her house (her house!) table.
She never told anyone exactly what the Hat had said to her.