Apart from being savagely vindictive and supremely confident, Julie must have been amazingly brave to do what she did to an innocent Jeremy.
A month after the massacre and Jeremy was a free man. An innocent Jeremy had not said anything to Julie. There would be no evidence supporting a guilty Jeremy.
Despite this she approached the police, and amazingly told unsupported lies to try to get the correct murder/suicide verdict overturned.
She would assume there was no evidence which would support her lies. Meaning she would get into trouble if found to be lying. Maybe she thought she wouldn't get found out and her testimony alone would be enough. Which was very very naive.
She was prepared to and went through with a WS and testifying. Knowing Bamber was innocent and a 'not guilty' verdict would ruin her.
Jesus, she was brave (and stupid).
Although I have to say she was also very brave in going to police after a month if Jeremy was guilty. As I just stated in another thread.