OG Hailey tried 3 times to change the future but failed miserably and then she decided to end herself to open the door for a new unknown future, hoping the ML, Lawrence and the Duncan family will survive.
She already knew FL will take over her body even before she died. Her diary entry for FL was the hardest thing to read in this story TBH. OG Hailey dumped the burden of the future to FL and was asking for forgiveness...
How come?? Until the very end, OG Hailey was remarkably selfless human being, she did nothing wrong and was genuinely trying her best to change the future. She fought the fierce battle by herself. Did everything she could, she also dealt with her abusive father. She did not need ask for forgiveness....
It was a cruel fate for her, from the beginning to the very end.

The only spoiler i know is- the og hailey was able to see the future- she saw many deaths or bad endings (?) but when she saw her self dying the future changed (it was unknown) so she sacrificed herself. Poor girl