I like that they hit on Fern and Frieren's overall interactions again here.

Frieren operates as a mother-sister-daughter at varying and cyclical times to Fern, and with as competent as Fern is, it is easy to forget that she is still an older teen budding into full adulthood.

Frieren probably always sees people in the light she met them in. She always thinks of Himmel in his prime (which is why she was shocked he got so old), Fern always a little girl. That old dwarf is always an old dwarf in love with his wife, so she took forever to notice that he has Dwarfheimer's.

Stark is lucky that she met him when she did.

I'm pretty sure she treats Sein as a kid because she thinks it is funny. On the other hand, he's middle aged, but still acts with youthful enthusiasm. That's why he has to go find Gorilla. They need to finally have their adventure together.