She didn't just fail to report a crime, she omitted an awful lost when she was interviewed by the police. She basically covered up for him - until he dumped her. Are we seriously to believe that she didn't mention any of the stuff she claimed he said to any of her mates before the murders?
If JB is guilty then she most certainly did more than fail to report a crime. There is ample evidence, if JB is guilty, that she was an accessory/accomplice to the crime.
I feel sure that if all the dealings between EP, JM and the NOTW were revealed then we would see exposed the plotting of a frame up.
Just to add to the many who have already said, it is good to see you posting again, Kaldin.