Eren's always been a bit odd.
Observing her you get the sense she's not really living. She's like a ghost, a hollow shell of a person.
The way she moves is fluid with all the lethal grace of a knife, but her movements are empty of life, devoid of purpose like an automaton simply acting out the movements.
Her grey eyes and pale skin make the comparison all the more apt. She's devoid of colour, washed out. Even her hair which was once lustrous brown seems now more grey, sapped of colour and life.
She might yet live but inside she is hollow.
She has another life, a new life. But Reiji isn't here and she is once more a ghost.
A phantom without an existence.
An: Inspired by the first opening Karma, and the cycle of rebirth associated with the concept.