Intriguing premise, leaning towards:
“A woman on the verge of suicide ignites a journey of reconciliation and self-forgiveness when replying to a 40-year-old letter from her imprisoned lover”
1. Refashion to better grab the reader concerning suicide, letter, and journey.
2. Who is this woman? E.g., a nurse that fell for a soldier that was captured. Prison guard? I would love to see the connection.
3. Changed letter(s) to one letter – her destiny needs only a single action to start her journey.
4. A location may help orientate the reader.
Hope you find this constructive, keep going!