It does seem sad that the family doesn't want these things mainly the diaries. But what you and I see as treasures and memories may not be how they remember their loved one. My mother, and grandmother have both passed away I had A LOT of stuff! Initially I kept a lot of it because of grief and how could I throw or give their belongings away? I eventually came to realize that I wasn't using their stuff. In fact it was cluttering up my space and collecting dust. The things I had kept were not my loved ones and holding onto them didn't really ease the pain of loss.
One Christmas I gave my grandma one of those Christmas houses that light up. She was so pleased with that gift and she HAD EVERYTHING so shopping for her made it hard. So every year after that I bought her a new piece for her collection. She adored it, she had a bakery, a church, a train station, the list goes on there were about 10 of them. She left a note for me attached to one of the boxes expressing how much she loved them and thought of me. This week I took them to Teen Challenge thrift store. Was it sad maybe to someone else. But to me the note which I had taken off meant more than the actually item. And the memories of her opening them on Christmas and seeing how delighted her face was at seeing it. The note really is the reminder to me.
My long winded story is coming to a point. It may be that because this woman was so proficient and good at quilting that members of her family treasure something else closer to them than the books or diaries. The quilt she made them out of their old Christmas pajamas, or a wedding quilt. It may also be another entire aspect of her life that didn't involve quilting at all that they treasure.
As for those diaries if your state has a society that tracks quilts and their makers they may be interested in them. Those are important, and truly that is what I would have kept if I was a non-quilting family member.