Let's start with the physical. There isn't a lot of detail for this one. Most of the story/poem deals with her feelings and actions. First, Kim Ha is a girl. Second, she is young: 10 years old.
Her personality is more interesting. Ha is not one to back down from her brothers. She is slightly mischievous. Of course if you asked her brothers, they might call her annoying. If she can't compete with them, she becomes a bit devious. Read the following quote.
"I can't make my brothers
Go live elsewhere,
but I can
hide their sandals."
If you have a younger sibling, I'm sure that sounds familiar. If you are the younger sibling, I'm sure that sound very familiar. Perhaps she does these kinds of things in an effort to establish some kind of control in her life. I don't think she does it to be a pest or a bully. She's been uprooted from everything that she knows. She's in a new place with new people and new customs. She is treated as different and harbors some resentment at being moved. She can be a bit bitter about having her world turned upside down. The shoe thing is one way to establish control over something . . . anything.
Ha is not always a pest, though. She is incredibly empathetic to her brothers. She can be happy for them and she can be sad with them and offer them comfort. At one point her brother's dead chick is discovered. Rather than act repulsed by it, Ha wraps the chick in her doll and throws both of them into the ocean. She sacrifices her most prized possession to help comfort her brother. That's amazing, especially from a 10-year-old. It shows that she cares deeply for her family and loves them dearly.