In "Lamb to the Slaughter," how is Mary different at the end of the story?

In a moment, Mary Maloney transforms from a woman who lives to please her husband to
one prepared to do anything to save herself and her unborn child. That moment is well-captured
in her thoughts immediately following the murder:

What
were the laws about murderers with unborn children? Did they kill then both-mother and child? Or
did they wait until the tenth month? What did they do? Mary Maloney didnt know. And she
certainly wasnt prepared to take a chance.

Once she
learns that her husband plans to leave her, Mary Maloney's world changes. She reacts
unexpectedly in a moment of blinding anger, killing Patrick with one blow. And afterward, she is
not filled with remorse for the love she has lost. Instead, her emotional loss for the
relationship she believed in prior to that moment leaves her with a void that she replaces with
self-survival and protection for her unborn child at any cost. Thus, she quickly develops a
calculated plan to craft an alibi for herself, seamlessly...