Hi, I was just rereading this whole series once (can't wait for the new book!) and I think there might be a plot hole?
So, diary Riddle tells Anna that she has to die, blah de blah. But how did he know that? He doesn't have any memories of the future. Heck, he didn't even know that Harry defeated the future Voldy on Halloween in Godric's Hollow until Ginny tells him about it. So how does he know something that Ginny couldn't ever have known, that Anna herself didn't know?
It could have been possible that he had some connection to his future self, the prime Voldemort and that the future Voldy knows about Anna and, by extension, so does Riddle. But Voldemort doesn't feel the diary getting destroyed and neither does Diary Riddle feel Voldemort getting defeated. So that isn't possible too.
How. Does. He. Know?
If it was intentional, then could you clarify it?
Love this series, it is a unique addition in the whole trope plot line of Harry's younger sister :)