She lives with her parents and siblings, but her father (Marco Ricca) is often away.
She contrives a reason to meet the other Irene (Isabella Torres), who is much more extroverted and self-confident, but calls herself Madalena, the name of her family's live-in maid.
At home, Irene starts behaving out of character, for example by calling her father by his first name instead of Dad, and telling Madalena that she has kissed a boy, when in fact it was the other Irene who kissed him.
However, part way through, she makes up some clearly fictional elements, so the rest of the family thinks that the entire story is made up.
In the final scene of the movie, the two girls swap places, to the consternation of the respective mothers.