Hello chinapanga
I'm sorry but I haven't got a death or burial for Elizabeth wife of George, but I wonder if you have tried the parish records for St Mary's? Most of the Tattums seemed to use St Mary's Bagillt and the Flintshire archives has burial records for the church for 1839 - 1944 or p'haps someone else has access to these records and might be able to help. There could well be several Elizabeth Tattums, but the records might record Elizabeth, wife/widow of George and give an address which might narrow it down.
I wonder if you could clear up something for me? Mary, Ann's sister, was, I think, witness to the marriages of her sisters Margaret and Ann. I had originally thought that Ann was also a witness to Mary's marriage as an Ann Tattum was a witness - but Ann should have been Ann Hughes when Mary married in 1864, so it can't be your Ann. Have you come across another Ann Tattum who could have witnessed Mary's marriage?
Regards, Ninian