I am actually reading them right now on another board. They sound as if she were a stenographer, very point by point. They also sound as if they were written some time after events, and they sound as if she is writing FOR someone - like a time-line.
To me it doesn´t appear to be a young person´s diary. It is a bit.... off.
P.S. as an example she writes on the page of August 17: For a day we were quite happy. If she had written the diary day by day wouldn´t she say something like: The day was quite happy - or: Today was quite happy.
Another thing: There is an entry on"August 6" (she couldn´t have known then, could she?

):
"Night/morning of 5 murders at Tolleshunt D'Arcy.
- White House Farm
1) Mr Nevill Bamber 8 x 's
2) Mrs June Bamber 5 x 's
3) Mrs Sheila Caffell All shot twice (suicide?)
4) Nicholas Caffell 3 x 's
5) Daniel Caffell 3 x 's"
It sounds like something a police officer would write, "Mrs Sheila Caffell", "Daniel Caffell".... Julie knew them, she would have written "Sheila" and "Daniel" etc.
Why so formal?
Not her diary - something concocted in collaboration with EP. Some of it undoubdetly true, some not.
Lastly, if this is not a day-by-day diary, we can see by the dates it isn´t, why use a diary with those dates? Can´t help thinking it is to give it an air of authenticity.
Just thinking aloud here - and not very coherently.... LOL