It seems to show that Tara has built this world view of herself as being "unbreakable" because of the life she has lived so far and how she was raised. She seems to believe that she is "strong" and nothing could possibly hurt her. However the second this view is shaken by her brother, she develops this false narrative. Where she thinks his abuse was not effecting her and that in of it self was "its effect". She is trying to convince herself that the pain is not from her brother but the fact she even feels hurt from the abuse.