I can clearly recall this book featuring a princess who spoke with a very distinct accent. The main issue I'm having now is that I remember very little of this book now.
I know that I read it sometime between 2012 and 2014, but I'm unsure as to how much older the book was than that. That being said, it did seem rather recent, so I'd say it was published no earlier than 2000 but its publication date is likely much closer to when I read it.
The book itself was definitely a young-adult fantasy novel, possibly with magic-use though I can't remember the details of that now. The novel was narrated either in 1st person or 3rd person limited given that it only focused on the main character, who was a teenage boy. He may not have been from the same world that the majority of the story takes place in. I do remember there was some sort of conflict between two powers that I want to say were opposing nations or empires. The majority of what I recall is about the deuteragonist, the princess. I believe she was fairly close to the main character's age since he seemed to have a crush on her (or at the very least, a deep respect for her). She also was not from the same nation as the MC and possibly wasn't human. Her most memorable trait for me, though, was her accent.
She was presented as a character still learning English (or whatever language was being replaced by English in the story) and thus spoke with an accent. Special attention was given to this trait by the main character throughout the novel, often noting her unusual pronunciations or odd phrasings. However, despite English obviously being her second language, I can't recall there ever being any communication errors between her and other characters, which is important given how much of the climax revolves around her revealing that she knows much more than she's let on. There's a line in the book that specifically references her dropping her accent and speaking in very clear and complex English. I believe she may have also been spying on the kingdom she was living in or at the very least observing them, using the clueless foreigner guise to her advantage.
What really stuck out in my mind with this story was how well I was able to read the princess' accent and I'd very much so like to be able to revisit this book to not only see how well my memory of her accent holds up but to see how the author accomplished the effect, since it was rather impressive. Most attempts at representing an accent are strained, in my experience, and this one was very clear and easy to understand.