Yeah, it's weird and awkward writing. She is still a child acting massively un-child-like. She didn't gain memories of a past life. She wasn't reincarnated. She is still just a nine-year-old girl acting like an adult even though just a few weeks ago, she was a spoiled child. The only difference is that she read a book about the future and now believes it.
It's like she completely forgot that she's still a child. Scratch that. It's like the author forgot that Philomel is still a child and is just working off of clichéd tropes. Because that's what's happening.