In "The Stolen Party" by Liliana Heker, of what importance is the monkey?

The story is about a young girl named Rosaura who has been
invited to the party of a wealthy classmate.  Her mother does not want her to go because
she will not fit in at a rich person’s party.  Rosaura tells her mother “rich people go
to Heaven too.”  Her mother thinks she will just be seen as the maid’s daughter, because
her mother used to clean the house.

Rosaura is excited
because there will be a magician with a monkey at the party.  Her mother scoffs at the
idea, not believing her.  But she starches Rosaura’s Christmas dress and helps her do
her hair with apple cider to make it shiny.  When she gets to the party she asks about
the monkey and sees it in her cage.  The she is asked to bring a jug of juice into the
party.

Rosaura is accosted by a girl with a bow who demands
to know who she is.  Rosaura says she is Luciana’s friend and the girl tells her she is
Luciana’s cousin and she knows all of her friends.  Her mother has told her to answer
that she is the daughter of the employee if anyone asks who she is.  The girl with the
bow responds with dirisive confusion, and then  The housekeeper Sefiora Ines interrupts
and asks Rosaura to serve hot dogs.

Rosaura enjoys the
party, winning at the games.  Rosaura loves passing out the cake slices because she
gives the girl with the bow the smallest one.  Rosaura even assists the
magician. 

At the end of the party, Rosaura does not get a
present like the other children.  She gets paid.

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Sefiora Ines didn't look in the pink
bag. Nor did she look in the blue bag. Instead she rummaged in her purse. In her hand
appeared two bills.

"You really and truly earned
this," she said handing them over. "Thank you for all your help, my
pet."

Rosaura is
horrified.  She didn’t realize that she wasn’t at the party as a guest.  She was the
hired help.  She finally understands social class.