The 5th grader won't really understand the significance of what that will mean to her or her life. She is a child and views the world as something magical and the harsh realities that we adults live through is not apparent to her at this age.
She will need to understand that she is special and this unfortunate illness has taken a hold of her. She will need to know that her life won't be the same again but it is not a reason to not play and live life to its fullest. She needs to know that she is not different to anyone else and that this illness does not define her being. People may see her as such but that should not be her definition of herself.
She needs to feel safe.
