Why does Kathleen feel free when the soldier goes missing? Why is the betrothal "sinister"?

Kathleen Drover, a middle-aged wife and mother of three, recalled when she was engaged as a young woman many years before.  Her fiancé was a soldier during World War I.  He was a mysterious man. She was young and did not know him well.  Months after their August farewell, "her fiancé was reported missing, presumed killed." Kathleen suffered "a little grief" after she found out this news.  Her family was not sorry that their daughter did not marry...

Kathleen Drover, a middle-aged wife and mother of three, recalled when she was engaged as a young woman many years before.  Her fiancé was a soldier during World War I.  He was a mysterious man. She was young and did not know him well.  Months after their August farewell, "her fiancé was reported missing, presumed killed." Kathleen suffered "a little grief" after she found out this news.  Her family was not sorry that their daughter did not marry a "man they knew almost nothing about."  

Though Kathleen had said yes to becoming engaged to her soldier, the "unnatural promise [drove] down between her and the rest of all humankind."  She looked back on their engagement and realized that she "could not have plighted a more sinister troth."  It seemed as though she said yes to him with hesitation.  This was evident because the engagement "made her feel so apart, lost and forsworn."  This meant that she felt as though she had made a promise she did not truly want to make or even intend to keep.  When the soldier went missing, Kathleen felt relieved.  She no longer had to keep that "unnatural promise."  The story did not indicate that she felt an immediate, long term sense of freedom.  She experienced a temporary freedom after she parted from the soldier to run to the safety of her home and family.  In the long term, she was single for many years.  A sense of foreboding stayed with her.  She eventually got married as a woman in her early thirties.  She settled into the routines of life with her husband and children.

The betrothal was "sinister" because of the regret Kathleen felt about it. It was also sinister because of her fiancé's parting words, which had a foreboding tone.  He told her that he would always "be with [her]."  He also pressed her hand against his sharp buttons until she was cut.