"I didn't like the sight or the feeling of families being separated", Trump said.
According to the first lady's communications director Stephanie Grisham, there's no "hidden message" behind the jacket.
Acting or commenting from the sidelines apparently was not enough for Trump, who fewer than 48 hours ago informed her staff - and her husband, the President of the United States - that she had decided she needed to see for herself the family intake and unaccompanied children facilities. On the wall was a handpainted American flag and the children signed it.
"They're the worst immigration laws in the history of the world", Trump said. She asked many questions, seeking assurances that they are being properly cared for. They attend school five days a week and have a variety of activities. Media also agreed to limit photographs during the visit of the facilities to protect the privacy of the detained children.
The trip was meant to lend support to some of the more than 2,300 children who remain separated from their parents, Grisham said.
Mrs. Trump's plane landed in McAllen in a heavy downpour.
"We are pleased that the president is calling a halt to his inhumane and heartless policy of separating parents from their children", said Peter Schey, the lawyer in a lawsuit that resulted in a key agreement governing the treatment of migrant children in detention called the Flores settlement.
For weeks, Trump had insisted he was bound by law to split children from their parents and that only Congress could resolve the problem - before he radically shifted gears.
More than 2,000 children have been separated from their parents since April, when Mr Trump's attorney general Jeff Sessions instituted a "zero tolerance" policy.
Top House Democrat Nancy Pelosi said her caucus was opposed to both bills, and it was unclear if there was sufficient Republican support for the compromise measure.
The former model's press secretary Stephanie Grisham said Melania chose to make the last-minute trip to witness the ongoing border crisis firsthand. She told her staff she wanted to go and we made that happen.
Santa Fe Mayor Alan Webber said the Trump administration can not easily repair the emotional trauma inflicted on immigrant children and that the president's executive order doesn't fix a racist approach to immigration policy. "We are all bothered by it".
Grisham said that the first lady had the full backing of her husband.
On Thursday, she had "boots on the ground" in Texas.
The spokeswoman said she does not know whether the first lady's own background as an immigrant affected her thinking.
"My wife feels very strongly about it", he told reporters after he signed the order.
The pair of statements from the first lady amounted to an unusual public intervention by Mrs. Trump into a policy debate.
"I'm glad I'm here and I'm looking forward to seeing and meeting children, but first of all let me begin to recognize each of you and thanking you for all that you do, for your heroic work that you do every day and what you do for those children", Melania Trump said.