There is no dispute that Julie badly betrayed Bamber at least five times while they were still together.
The betrayal started on the 27th August 1985 & put him at great risk of being arrested and charged if other informed people went to the police.
It has been suggested that Julie started talking to other people while still with Bamber, because the relatives spent 20 days filling her head with suggestions of his guilt.
There are several reasons why the relatives could not greatly influence Julie in these 20 days -
The relatives did not know Julie very well.
The relatives were intially grieving & supportive.
The relatives at first focused on engaging with several police.
Julie was Bamber's girlfriend so unlikely to be receptive to the relatives suggestions.
Bamber had 24/7 access to Julie so able fo constantly influence her.
Julie may have been in on the crime. So again would not respond.
Julie was with Bamber virtually all the time in these 20 days so not contactable.
Bamber & Julie spent most of the 20 days outside of Essex so again not contactable.
The relatives did not want to alert Bamber that they were suspicious of him by contacting Julie.
Julie may not know anything so only disadvantages in contacting her.
If Julie was influenced by the relatives, there was nothing she could do anyway.
Any possible face to face contact with Julie, such as at the funeral, Bamber would also be present.
There were no mobile phones in 1985. The relatives would not know Bamber's & Julie's locations when out of Essex.
It would be a massive undertaking to convince Julie. Perhaps taking up hours or days.
Secretly trying to start up communications with Julie puts her at risk if Bamber found out.
Engaging with Julie would suggest the relatives were plotting against Bamber.
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Hopefully everyone will agree the only person who influenced Julie in those 20 days was the man who rang her 3 times either side of the massacre.