the daughter of Agatha D-H.
The Emailaccout belongs to WhiteWicca1952, so we can assume, she was born in 1952. What corresponds with the pictures we see. In 1965 she must have been 13 years old and Agatha never mentioned a little daughter (or a daughter at all) in her diary.
In one Email the White Witch mentions Agatha D-H and shows great despite.

I read the messages the White Witch left at the cafe once more. You are right, she wants us/the journalist to help restore Baibins treasures. She even talks in an Emai to Mia that Baibin needs her treasures restored.
How could i not seen this before!

Elsie is Harker's daughter. For all we know, Harker could have had three or four children all safely lodging with the vicar in St Awful or tucked away in boarding school and having a better time of it than they would have had with a globe trotting, glory seeking mom more concerned with the monetary worth of a find than its scientific or historical value. That said, I got a kick out of Harker's journal, loved the photos (Was that someone in drag as Harker?) and loved how much clout Harker clearly had with the Royal Society. She must have been something of a celebrity archaeologist, not at all the type to be bothered by leaving her children with the grandps for years on end. I quite liked Harker with her Bronze Age pelf around her neck and her nose in the air. "Kids, what kids? Oh, those. Yes, must remember to write after Christmas and see if their camel ever arrived from Cairo. Perhaps the Pony Club will refrain from fussing if Elsie has a nonregulation mount." If taxed about leaving Elsie to the care of others, Harker would have sniffed and said, "Winston's moral compass was his nanny. Pass the cucumber sandwiches, there's a dear."

5-8 was easy enough.
I deduced 2,3,4 were together.
It's the first one - burning of leaflet that I went through inserting in between 2-4 by trial and error.

As for the grave thing - that was straightforward.
You have the list of grave things inserted in Agatha's journal plus the rolled up drawing of the location of those 4. See the walkthrough for pics of both of them.