Right now, with no information, i am going with Drizella killed Anastasia accidentally because Anastasia was the favorite daughter and Drizella was not.
Considering what both Adelaide and Gabrielle said in that EW article, I could believe that Drizella’s responsible in some way for her death. Adelaide does imply that at the time of that interview she didn’t actually know all the specifics, but both actresses seemed to be on the same wavelength of Anastasia having been the favoured daughter in a major way.
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