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Ok i cant believe i actually read this already lol so i pretty much know the ending but i think it was when before she died she received "god's call" and this person asked her what her wish would be, i believe her final wish was to have a dream because she wants to see her loved ones in her dream, her son and kuhn too. Although i think this is also the reason how she returned to the past too.

Whenever the 'future' dreams appear i always get scared... I saw someone make a theory before saying that these dreams are her reality and the "great wish" is her romance with the ML as well as fixing stuff, which basically means all thats happening aint real (since it seems like shes sick in her 'futuristic' dream) and shes just dreaming the plot of the whole manhwa, if that makes sense.... I kinda think its possible but i rlly hope not oml im so worried if anyone can spoil, pls dooooo smh that theory rlly stuck to me like damn, makes sense, but damn...