Lyra’s dialog in this series is written with alternative spellings, which suggest an accent. “Don’t know” is “dunno”, “ain’t” is “en’t”, and there are several others. She is supposed to have been raised by scholars at Oxford (albeit in an alternative universe’s version of Oxford), but has an accent different from them. My best guess is that it’s supposed to be a Norfolk accent.
I’ve been reading this series out loud, and I’d like to give her accent a go. (Don’t worry. I have a small and extremely forgiving audience.) Any help identifying and then learning it would be greatly appreciated!