Dang, what a plot twist. Current Athy is actually the Original Athy who executed on her first life. She just forgot it and only her 2nd life memories remained.
However, I think in her 2nd life, she remembered her 1st life that's why she suffered despair, depression and mentally unstable... In this 3rd life, I bet she used her magic to only remember her 2nd life in Korea and manipulated her memories in thinking that her 1st life is just an "online novel" she read before.
This explained the reason why she transmigrated, she actually have the power to travel through time.