Is Mary Maloney the lamb in Roald Dahl's "Lamb to the Slaughter"?She is the lamb because of her weak-mind and innocence. When she's sewing & trying...

It seems as if you have misinterpreted Mary Maloney's
character.  First, the title of the story does not imply that a lamb turns into a
slaughterer; rather, it represents an innocent creature being led to its death--that
does not describe Mary.

While Mary does "slaughter" her
husband, it would be more appropriate to argue that the police (her husband's comrades)
are the lambs.  When the story opens, Mary's husband, a police officer, springs the news
on his pregnant wife that he is leaving her.  If you keep in mind the time setting of
the story, you see that Mary views herself as the dutiful wife who waits for her husband
to come home each day, hangs on his every word, caters to his every need, and then he
repays her in such a manner.  Divorce during the Maloneys' time would have still carried
somewhat of a social stigma especially when coupled with Mary's pregnancy.  As the
reader considers that all these thoughts fly through Mary's head as her husband talks,
he must admit that Mary's quick action--while reprehensible--is hardly that of an
innocent lamb.

Similarly, after Mary murders her husband,
she uses her innocent appearance and demeanor to fool the grocer and the men who would
have known her husband best.  In contrast, the police who show up to Mary's house might
as well be figurative lambs going to the slaughterhouse.  They pander to Mary's needs
and comfort her, refusing to see her as a suspect, and they eat the murder weapon to
appease the "distraught" young widow. Their failure to look past Mary's outward demeanor
demonstrates that they are the ones with the herd mentality.