You bring up an interesting point that I hadn’t really thought of before. The fact that Fern is being raised through her adolescence by Frieren must have an impact on her. Frieren does not really seem like the type to be emotionally supportive as Fern is dealing with a tumultuous world around her on this journey. It would probably make Fern a bit weird to other humans as she has certainly picked up aspects of Frieren’s personality that have rubbed off onto her (just like Fern has influenced Frieren).