I have to disagree She said she knew he had done it on the night -then he told her the next day and all the gruesome details about how the hit man had done it and the hit man had made the call. that's when she should have done something .
You are arguing what she morally SHOULD have done. No one disputes that if you are aware a love done committed a crime turning them in is the just thing to do but no one can know what they will do in such a situation and plenty of people do the immoral thing of playing dumb or even actively trying to help their loved one escape liability for crimes. They don't want the pain of losing their loved one to prison.
Their are exceptional people who don't bat an eyelash and immediately turn in their loved ones even their kids. But most take time to decide what to do and many end up deciding to turn a blind eye and remain silent. Others decide to actively help protect them.
Until actually in the situation no one can know what they will do. I've been robbed in the past and I pulled a knife on the perp and literally scared the piss out of him. I KNEW what he stuck in my back wasn't a gun though. I just knew from the feel of it that it wasn't. It wound up being a stubby cellphone antenna. Since I knew it wasn't really a gun and that I had a knife I had no fear in confronting him. I have had training disarming people. I still can't know for sure how I will react in a situation where someone robs me and I know they have a gun. I wasn't in that exact situation before so can't predict my reaction. Practice disarming with a fake gun is not the same as trying it with a loaded weapon.
There is no such thing as practicing for the emotional turmoil involved in ratting out a loved one. The choice is easier in a situation where your loved one is a psychopath who rapes and murders at will and will keep doing it. In a situation where you think it was a one time thing and the person poses little threat to anyone or only a threat to gangsters and people you can rationalize as being deserving it is harder. Julie didn't think Jeremy posed a danger to anyone else. He had his family killed for money. She didn't see him being in that kind of a position ever again.
Through college and law school I knew people who shoplifted, did drugs and other illegal things. Did I run to police to rat any out? No. If I knew anyone who was guilty of a violent crime that would have been different that is significant enough to rat out but what if the person is extremely close to you and them being in prison will pain you greatly? What do you do then it is a quandary.
One of the best lines in Scent of a Woman was when Pacino said, "I always knew what the right path was. Without exception I knew. But I never took it. You know why? It was too damn hard." It is so poignant and easy to remember because it is often true.