I thought her first life was the original timeline of this story where she was killed, and in her second life she was a normal person in this world who read the novel that basically described her first life but from either a third persons perspective or the protag's POV. and this is her third life where she rememberers both previous lives of hers, meaning she knows about what's going on with the people around her (bc of 2nd life, reading the novel) and she also knows how to navigate her own situation due to her experiences and memories from her 1st life.