This is the 1937th most frequent Portuguese word.
luísa
"Luísa" is a Portuguese feminine given name, equivalent to "Louisa" in English.
Here 'Luísa' is used as a proper noun to identify an individual by their first name.
Luísa é minha amiga de infância.
Luísa is my childhood friend.
In this sentence, 'Luísa' is used again as a proper noun to refer specifically to a person in conversation.
Ontem falei com Luísa sobre o projeto.
Yesterday I talked to Luísa about the project.
The article 'A' before 'Luísa' signifies the specific person, Luísa, often used to express familiarity or emphasis in Portuguese.