This is the 2634th most frequent Polish word.
została
"Została" means "she/it became" or "she/it was left."
In this sentence, 'została' is used to indicate that the action of reading the book was completed in the past, akin to the passive voice in English.
Książka została przeczytana w ciągu jednego dnia.
The book was read in one day.
Here, 'została' signifies the change of state or becoming, indicating that she assumed the profession of a teacher after graduation.
Została nauczycielką po ukończeniu studiów.
She became a teacher after completing her studies.
In this example, 'została' expresses the occurrence or formalization of the decision in the past, describing a concluded action.