
In the first chapter of the novel, before "Athanasia" was reborn she said that "Is it because the 18 year old princess who ends up being killed by her father has the same name as mine?" So does that mean that the "Athanasia" in the present world who read the "Lovely Princess" novel was actually the real Athanasia?
It was also showed in a flashback where Jeanette was introducing Ijekiel to the past Athanasia, and when ijekiel saw Athanasia his eyes were mesmerized by athanashia, his eyes were like an anime character falling in love at first sight. Athanasia also said that It seems that she's felt it before.
I'm sorry btw I'm bad at explaining

This won't really answer your q but basically, in "lovely princess", Jeanette did a time-reversal spell that only she could do. so basically her memories would be removed and athy would be loved by Claude. the magic entity doing this thought "Claude is supposed to love athy. will it count if the body is hers but the soul is another." thus that entity made the "lovely princess" book. The body that the soul of Athanasia in present time was working and found that a customer left the book I think. she read it (it ended when athy died)and a little later she died leading to the medieval athy body and the present time athy soul. I honestly dont know about the second part sorry i hope it made sense tho Σ(  ̄□ ̄||)
The fact that Herrace died for Ariel and then when he passes the girl he loves calls another mans name like wtf giiirrrl