That's rather a generalisation and how one reacts to a psychopath depends on individual differences. Also, Julie didn't live with Jeremy so she was able to break away on a regular basis.
I don't think any of us can say why she didn't report Jeremy straight away - fact is she didn't but she was instrumental in his conviction and that's the main thing.
It also depends of the levels of psychopathy.
There are numerous reasons I firmly believe Jeremy Bamber to be a psychopath but more importantly if any of us go back and read his police interviews, evidence given in court etc - in other words his factual evidence; if he were telling the truth the facts would have remained the same. They haven't.
There are numerous factual inaccuracies that Jeremy Bamber has clearly manufactured in order to suit his end at that given moment.
And let's not forget, Jeremy Bamber has never publicly commented on Julie Mugfords wealth of evidence against him. Why not?
He's had 32 years to pull apart her witness statements but he's never done so.. He says he has been through his case files with a fine tooth comb and let's not forget he's had decades in which to so.