Might I be a complete spoilsport and discount the theory of Hermione having a favourite teacher at all?
Firstly, it's worth thinking about who Harry's - or more crucially perhaps Ron's - favourite teacher is. One of the great aspects of Hogwarts, as rightly pointed out to me by the friend who got me into the books in the first place, is that almost all of the teachers are very cool and likeable. Flitwick, Sprout and McGonagall for example are all very cool in their own ways. If we look to Harry's favourite teacher, the only two who would appear to rise above the rest are Lupin - who by Lupin's friendship with James and Harry's Dementor circumstances is naturally closer than the other teachers would be - and Barty Crouch Jnr, who we can rather safely rule out. Even when they are protesting to Umbridge about Lupin's brilliance, he is referred to as being the best DAtDA teacher they ever had, not teacher generally (I believe, from memory, it is Dean who says this, but it doesn't really matter to the wider point). The question of favourite teacher is never directly raised in the books because the overall quality of the teachers was very high - excepting only Snape, Trelawney, Hagrid perhaps, Binns and the DAtDA maniacs. This, of course, does not resemble education generally at schools (or at least at mine), which have long since been filled with all kinds of morons - some seemingly from birth, some who have evidently had the joy of teaching slowly crushed out of them - with a few gems. Naming my favourite teacher at high school is a great deal easier than naming Harry's, because while he might have been just as good as the Hogwart's lot, his competition was decidedly less fierce.
Then, of course, we have the fact that Hermione is a gifted and hard working student who takes extremely well to the practice of self-study. For her more than anyone, the attraction of a subject will have little to do with the teacher in question. Arithmancy may be her favourite, but she spends a great deal more time studying her subjects out of lessons than within them - as the library appears to be her natural habitat. I think that Hermione
respects all her teachers, and barring Umbridge and occasionally Snape, probably
likes them all too. Worthy of note is her natural reaction to the Grubbly-Plank led lesson in OotP, where she very much enjoys the lesson even though it insinuates that she prefers anyone to Hagrid, a close friend.
So, in conclusion, I don't think she has one. Sorry about that.