Esposa

Do not think there is a minimum stay. Many tourist fly into Foz do Iguacu or Puerto Iguazu, AR and go to one side of the falls to another for 3 hours.
May get a question as to "how will you stay?" upon arrival.

Lcarp1551 wrote:

My wife is from Sao Paolo, she is retuning to Brazil this month. She has been going back and forth on a Tourist visa. Is there a minimum she has to stay in Brazil before she can return to Michigan, USA?

You seem to be asking about the terms of a US tourist visa; you might get better information posting your question on the US board.
My Brazilian spouse also travels to the States on a tourist visa, but since he's never spent more than 90 days in the country during any calendar year, we've never had an issue.

I also am a little confused. You said she is from Sao Paulo on a tourist visa.
So is she a brasilian with a US visa or a US citizen with a Brazil visa?
Brazil tourist Visa is good for 10 years but can only stay "x" amount of days per year.

She is brazilian, we married in US, she has been staying here 6 months and Brazil 6 months and she has a tourist visa

She is a Brazilian Citizen?
A US visa must be valid at the time a traveler seeks admission to the United States, but the expiration date of the visa (validity period/length of time the visa can be used) has no relation to the length of time a temporary visitor may be authorized by the Department of Homeland Security to remain in the United States. Persons holding visas valid for multiple entries may make repeated trips to the United States, for travel for the same purpose, as long as the visa has not expired, and the traveler has done nothing to become ineligible to enter the United States, at port-of-entry.