How does the author use an internal dialog to develop Sophie's character?

The story is divided into narrative and dialogue though there is much more narrative because Sophie spends a great deal of time alone or only with the bonobos. In some cases, Sophie imagines conversations. For example, she interprets one of Otto's actions as having a particular meaning and will imagine the words he would have said, if he could talk. These “conversations” are set apart with italics, indicating to the reader that she's imagining them and that they aren't true words being spoken. In some cases, the italicized words belong to Sophie, as is seen when she is trying to mentally reassure Otto after he's caught in the snare.