Totally agree David. She had already said that she knew Jeremy was the killer without supernatural powers. Probably something to do with the drugs she was on.
She probably did in her heart, though admits only to realizing after call 2 that Jeremy was telling her his family was dead. Unable and unwilling to accept that the relationship had expired with them she went along with this narcissist until the pain became too great: as Julie put it she was carrying the guilt for both of them. It was not Julie chuckling behind closed doors at Bourtree Cottage but Jeremy: chuckling at the twenty five shots he fired, chuckling at the false trail he had set Police and chuckling at the thought of outwitting the relatives over whom he now had the whip hand and to whom he declared "I'm the boss", along with Police and Barbara, who found him with his feet up on the desk upon entering the office several days later. It was all make believe, a charade in Jeremy's mind that he would have the cash at his disposal at a time of his choosing, before he became staid and antiquated like the parents he had endured all those years, parents who had saved for a comfortable retirement, yet who met their nemesis at the end of a gun from a boy they had attempted to nurture the best they knew how.
How could Julie now accept the blood money of a wine bar in London's fashionable West End with five deaths on her conscience, how could she possibly pour a tomato juice to rich City slickers without memories of Jeremy flooding back, the superficial charisma hiding a terrible shallowness
ad interim which no materialism could sustain, and and as the noose tightened she did the only thing she could to extricate herself from this monster, the monster she may have in part helped to create, by finally divulging the extent of his defect to an outside source, though too late to assuage her conscience and the five corpses which lie lifeless thereon.
