[@Emma]
Oh, I'm so sorry, I was under the impression that her people had been on land for a few years now (the Oceana Abyssal's corrupted expansion drove them to land about 4 to 5 years ago), and while she wasn't perfect at reading and speaking- she was capable of it. That was a complete screw-up on my part. I assumed she was cloistered, but taught rudimentary things to survive. Maybe going this route would be best? That way she's still naive, but not so new to absolutely everything?

Like Life In Stasis (is Stasis cool to call you btw?) suggested it's possible that she could ask for the help of local inn-keepers if she couldn't read in common but could speak it. I think based on lore this would make the most sense. 

I have something that could explain the letter portion, but I don't really want to spoil it. Sooo I think this would work best.