Brewer, who has often clashed with the Obama administration over illegal immigration, made the remarks after touring a Border Patrol processing facility for new arrivals in Nogales, Arizona, with U.S. Secretary of Homeland Security Jeh Johnson.
More than 47,000 unaccompanied minors are thought to have entered the United States illegally between October and May, nearly twice as many as the year before, many of them fleeing poverty and gang violence in Central American countries.
"As a mother it breaks your heart to see the situation the children are in. And more so, that parents themselves put their children in harm's way," Brewer told reporters.
She said the center processed about 140 children every day, and that there were currently several pregnant girls there. Many would be released to illegal immigrant parents and later "blend" into society, the governor said.
"This crisis that America is facing is because we have not sent a strong message to these counties that our borders are closed. ... We need the federal government to step up and secure the border."
The surge in young arrivals has crowded facilities in Texas and led to efforts to move some to other states.
Brewer, whose administration in Arizona has taken a tough line on immigration, has slammed as "dangerous and unconscionable" a policy that in one instance saw hundreds of migrants detained in Texas released at Arizona bus stations.
President Barack Obama has called the flood of illegal immigrant children an urgent humanitarian crisis. It comes as a number of U.S. groups push for policy reform to allow the roughly 11 million undocumented immigrants in the United States to obtain a pathway to citizenship.
Many Republicans complain the federal government is not doing enough to secure the southern border, and they blame the surge of children on Obama's 2012 decision to give temporary relief from deportation to some young people brought to the United States illegally by their parents.
Johnson said that did not apply to children arriving from Central America, and that if they were apprehended at the border, they were considered a "priority" for deportation proceedings.
"We will stem the tide and find a solution to this problem, but until we do, we will deal with their kids in a safe, lawful and humane way," he said.