On what type of conflict (man vs man, man vs himself, man vs circumstance or man vs society) is the story "The Necklace" by Guy de Maupassant based?

Having served as a civil servant himself, Guy de
Maupassant often satirized the class to which these civil servants belonged.  Often his
works contain subtle social commentary.  Such a story is "The Necklace" in which
Mathilde Loisel is

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one of those pretty and charming girls, born, as
if by an accident of fate, into a family of clerk.  With no dowry, no prospects, no way
of any kind of being met, understood, loved, and married by a man both prosperous and
famous, se was finally married to a minor clerk in the Ministry of
Education.

In this first
paragraph, Maupassant already sets Mme. Loisel in conflict with society.  For she could
easily have been a lady had her parents been wealthy.  Consequently, she is as "unhappy
as a woman who has come down in the world" because she
possesses

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natural poise,...instinctive good taste, and
..[the] mental cleverness [that] make daughters of the common people the equals of
ladies in high society.

Thus,
because Mathilde Loisel realizes that she could be the equal of aristocratic ladies, she
is discontent and places excessive value upon material possessions as she perceives
monetary things being the means to higher positions in society.  This is why she thinks
that Mme. Forestier has loaned her a real diamond necklace, for in her mind, no wealthy
woman would possess faux diamonds; this is why she does not confess to Mme. Forestier
that she has lost the necklace.  She is too proud to admit such a fault, already feeling
inferior. 

Throughout the narrative of Maupassant's story,
Mme. Loisel sees herself as the "accident of fate" as Maupassant writes in the first
paragraph.  She is meant to be a lady, but is denied this role because she is the child
of a civil servant and has married a civil servant.  Her obsession with this idea
prevents her from appreciating what a kind, generous person her husband is, and what a
kind friend Mme Forestier has been.  Thus, Mme. Loisel's conflict with her social
position becomes internalized and is, then, an internal conflict of person versus self. 
Indeed, it is her pride that causes her to live the miserable years in payment for the
diamond necklace.