Someone else -- another creation of the AUC -- had found a use for her. Because he didn't see death a fitting end for her, he sought to punish her instead by imprinting her with one personality after another, sending her off to die over and over for several decades as different people. Though perhaps it wasn't punishment so much as he wanted to see her killed and suffer, while never being fully aware of it.

[Like she said, Firo. The details aren't much happier than Fiona's previous situation.]