What are the secret activities of the protagonist of "Felicidad Clandestina"? What is her objective? 

It is pretty obvious, and it is that the girl visited the house of the other girl who's father sells books. Clearly the protagonist loves to read and the girl is really trying to get the book she wants, but in secret as her parents do not know about it and it also would be weird telling them that she is visiting the house everyday. "El plan secreto de la hija del dueño de la librería era sereno y diabólico. Al día siguiente allí estaba yo en la puerta de su casa, con una sonrisa y el corazón palpitante". Her objective is to convince the bookseller's daughter to provide the books she wants to read.

References:

• Lispector, C. (1971) Felicidad Clandestina y otros relatos. Colección Antares.

Clarice Lispector (1920 - 1977) was a Brazilian novelist and short story writer acclaimed internationally for her innovative novels and short stories.