Hermione is part of the famous trio of the book- Harry, Ron, and her. Hermione is the main brains of the gorup. Sometimes she takes this to an extreme with her work. Harry and Ron think she overdoes it, but her grades reflect her hard work, and she is most likely the smartest student in her year.
Hermione has always helped a lot in the 3 friends causes throughout the book. She got the pass from Gilderoy Lockhart (whom she has a crush on), figured out what the Chamber monster was, and helped tremendously in their reseearch on Nicholas Flamel and the eventual resting place of the Philosophere's, or Sorcerer's, Stone.
If it wasn't for Hermione, Harry's adventures would have never been possible.