Final answer:
Katniss wrote her story to cope with her nightmares and trauma, to ensure the events are remembered, and potentially to aid Peeta and inform her children.
Step-by-step explanation:
In the Epilogue of The Hunger Games series, Katniss implies she wrote her story down primarily to help her cope with her traumatic experiences and nightmares. By documenting her journey, she can process her emotions and potentially alleviate the psychological burden they carry. Although not explicitly stated, creating a record ensures that the events are not forgotten, can assist Peeta with his memory struggles, and allows her to explain her past to her children someday. Out of the provided options, A) To help her nightmares seems like the most directly applicable reason as it aligns with her character's ongoing struggle to deal with the past.