This is the 2869th most frequent Portuguese word.
dona
"Lady" or "Mrs." (used as a respectful title for women).
In this sentence, 'dona' refers to the feminine owner or proprietor of the restaurant.
A dona do restaurante nos recebeu muito bem.
The owner of the restaurant received us very well.
In this case, 'dona' is used colloquially to refer to a woman or lady, often the one being talked about.
Você conhece a história da dona que mora ao lado?
Do you know the story of the lady who lives next door?
Here, 'dona' is used as a respectful form of address preceding a woman's first name, akin to 'Ms.' in English.