"She walks the dog" is usually used with a ring of a chore, task or something that is necessary to do.
With that ring, it could be translated (with no loss of meaning) into Portuguese as "levar o cachorro para passear/passeia com o cachorro, etc... OR até levar o cachorro para um passeio/para fazer o exercicio dele (o cachorro).
I learned that there´s also the "walk(ing) the dog" an expression from basketball, meaning
An offensive player giving the defensive (player) something else to think about and, in that way, giving the offensive one some advantage. That is, he uses an strategy of the chess, only that he doesn´t sacrifice anything, but uses distraction!