In John Boyne's The Boy in the Striped Pajamas, what does Gretel look like?

While we
are not given a direct description of Gretel's appearance in the novel, here are some details
about her character that may help to form an image of Bruno's older sister for you:

In s novel , in addition to being repeatedly referred to by her
brother Bruno as a Hopeless case, and, at the beginning of Chapter 3 as nothing but trouble,
Gretel is further described in that chapter as Brunos older sister by three years, as the
following text from the book demonstrates:

Gretel was
three years older than Bruno and she had made it clear to him from as far back as he could
remember that when it came to the ways of the world, particularly any events within that world
that concerned the two of them, she was in charge.

As
Bruno is described in this chapter as being nine-years-old, that, obviously, makes Gretel
12-years-old.  While Bruno clearly chafes at life under the domineering...