She meant that she was able to comprehend what was written in the Eastern culture and how they cook and do things? Well she didn't actually said that she had read it in some type of book, but let put it this way if you know thousands of languages and you're in the medieval period obviously it would mean that you know their culture since you're able to speak their languages since they don't have internet they would read a lot of books and who knows what you might discover in books like their cultures or something (which is the reason she discovered she can understand different languages)

Bruh how is the fact that she's a polyglot explain how she knows so much about the east's culture lmao
Like I would say I'm fluent in spanish but ik fuck all about latin american countries