Harry Potter and the Deathly Hallows
Affiliation: Order of the Phoenix
House: Gryffindor, 7th Year
In a 2006 interview, a fan asked Rowling what Hermione would see if she looked into the Mirror of Erised, which reveals a person's deepest desires. Here's how Rowling responded:
Well, […] at the moment, as you know, Harry, Ron, and Hermione have just finished their penultimate year at Hogwarts and Hermione and Ron have told Harry that they're going to go with him wherever he goes next. So at the moment I think that Hermione would see most likely the three of them alive and unscathed and Voldemort finished. […] But I think that Hermione would also see herself closely entwined... with... another... person […]. I think you can probably guess who. (source)
And we're happy to say that in Harry Potter and the Deathly Hallows, both of Hermione's deepest desires are fulfilled – she, Harry, and Ron see Voldemort defeated, and she and Ron finally get together. But Hermione sure has to work hard in Book 7 to ensure both wishes come true.
Organizer and Voice of Reason
Hermione really shines in Deathly Hallows. Here we see that she's grown into a strong, independent, and markedly less neurotic character than she ever has been. While, earlier, Hermione was more than a little crazy at times, here she seems to have figured out how best to use her organizational and research skills in order to keep Harry and Ron safe and, for lack of a better word, under control.
It seems at times (as it always has) that Hermione is way ahead of Ron and Harry in terms of growing up; she's always been the voice of reason, and this is still her role here. However, her relationships with both Harry and Ron have developed and matured, and the boys both recognize that this voice of reason is one that they should listen to carefully. Though Harry and Ron have more dramatic conflicts to resolve, Hermione is, in some ways, the leader – she's the one who's figured out the practical concerns of their voyage, and she does so with a quiet maturity and confidence.
That's not to say that Hermione has an easy time in Deathly Hallows. Far from it, in fact. As a Muggle-born witch, Hermione is in terrible danger while Voldemort is in power. The Death Eaters are essentially bent on committing genocide and getting rid of all witches and wizards like Hermione – those who were born into Muggle families and therefore lack a "pureblood" history.
Next up, when Harry, Ron, and Hermione are captured by Fenrir Greyback & Co., it's Hermione (the "Mudblood") who gets questioned and tortured. We hear her shrieks of pain as Bellatrix uses the Cruciatus curse on her, and then see Fleur nursing Hermione back to health with the use of Skele-Gro. Of the three friends, Hermione is the one that suffers the most physically this time.
In addition to being a target for Death Eaters, Hermione places herself in extreme danger by joining Harry on his quest. She makes a great sacrifice by joining him and sticking by his side the whole time. She even uses her magical powers to brainwash her parents into thinking that they don't have a daughter, and gets them to move to Australia, to stay well out of harm's way.
Hermione and Ron
For all of Hermione's intelligence and bravery, she can't be solid and mature all the time. As we've noticed for the past several books, she and Ron have feelings for each other that just can't be contained, and Ron's departure is easily the darkest time for poor Miss Granger. Yet she manages to keep the quest at the forefront of her mind and keep trekking along. But her emotional turmoil is all unleashed when Ron returns; only then does she reveal exactly how upset she was by his disappearance, and also how much she cares for him. Hermione's always had some trouble getting her head and her heart to work together, but here, she's grown up enough to let herself admit to her feelings (not just her intellect). In the end, it's Hermione who takes the first step and kisses Ron – after he shows concern for Hogwarts' house-elves, of course.
In the Epilogue, we see Hermione married to Ron and sending their daughter Rose off to her first year at Hogwarts. We've also learned that Rose has an intellect to match her mother's – we wish we could see that in action. And if you find yourself craving a few more of the details of Hermione's path, here's an extra tidbit from Rowling:
Hermione began her post-Hogwarts career at the Department for the Regulation and Control of Magical Creatures […] where she was instrumental in greatly improving life for house-elves and their ilk. She then moved (despite her jibe to Scrimgeour) to the Dept. of Magical Law Enforcement. (source)