Ok, I've been swearing up and down she is ISTJ with
highly developed Fi in the books as opposed to maybe ESTJ in the movies... I'll copy a post I made at another site to show my thinking...
I think she's ISTJ in the books, (though probably a little more outgoing than the typical ISTJ) but ESTJ in the movies, helped along by Emma Watson supposedly being ESTJ. I guess I see her passion for elf-rights, among other things, as pointing to higher-up than inferior Fi. She's really clear on what she values ("There are more important things-friendship and bravery") and she is continuing to shape her values as she grows older to be more nuanced, she saw that Winky was treated as a non-person by the wizarding community, she wants to do some good in the world and that's really important for her career choice. Inferior Fi I think is usually more general in what they value (Truth! Justice! Doing What's Right!) and doesn't want to spend as much time dwelling on it. I see inferior Ne more likely, she's a genius at remembering stuff from books she's read, yet can seem suspicious about unconventional methods, she didn't like the Half-Blood Prince's notes because that wouldn't be following the instructions, she often freaks out about all the ways things can go wrong, the usual way of inferior Ne, for example if the plan isn't followed, or if she fails her exams or if they're caught and expelled, etc. I thought she was much more decisive and assertive in the movies.
but now I have this crazy idea that maybe she is INFP in the grip. She seems to grow somewhat out of being bossy as the books go on, even in the first book she bent rules for Harry and Ron (Somebody's Fi value system might put friendship before rules) Is she Te as a method of coping with various stresses such as being a Muggle-born witch and looked down on, insecurity, maybe difficulties with her family? She gets easily offended when things go against her morals. INFP would still give her tertiary Si, so all the obvious genius uses she makes of Si could be a lower function? Tertiary Si types INFP and INTP often are pretty routine oriented. (One of the reasons they mistype as J's) When is she more herself and happier, more balanced? When she's living up to her beliefs (Fi) and using Ne to keep herself open to new perspectives? For example when she first starts S.P.E.W. in Book 4 it may resemble an Fi-Si loop, she gets caught up in her values and how a movement to make things better 'should' go, perhaps based on movements she's read about in the past (Si). But in books 5-7 she meets Kreacher and while still caring passionately about helping the elves she takes more time to understand their perspective and consider different sides of the situation.
J.K. Rowling said Hermione was somewhat based on herself as a kid, and yes that does not necessarily mean they are the same type as different types could exhibit the same behavior for different reasons, but think about it. If J.K. Rowling, who I am pretty confident is INFP, (INFP-INFJ is a very common mistype) could have acted, according to her, even more bossy than Hermione at age 11, consider that its not impossible an INFP would be like Hermione.
Feel free to throw tomatoes at this, but what do you think? Is this an insane idea generated by sleep deprivation or could there be something to it?