The reversal came after U.S. Customs and Border Protection received inquiries from The Associated Press and other media about the case.
Federal authorities have sent more than 50,000 migrants — including people who crossed the border legally — back over the border to wait for their court dates in Mexican border cities under the Migrant Protection Protocols.
The girl was born in Honduras with colon problems and has had several surgeries since birth. Her mother told the Associated Press that they left Honduras in hopes that they could receive better medical treatment in the U.S.
They crossed the border without authorization. According to a doctor who later examined the girl, she developed a fistula while in CBP detention between her colon and her skin while in detention, which caused her stool to leak. She wears a diaper.
U.S. Customs and Border Protection declined to comment on the girl's case.
Global Response Management, a nonprofit that runs a sidewalk clinic for people living in Matamoros, Mexico, says border agents took the girl to the emergency room of Valley Baptist Medical Center in Brownsville. She was briefly seen and then returned with her mother to Matamoros.
The Associated Press is identifying the mother by only her first name, Isabel, and withholding the daughter's name at their lawyers' request because they fear for their safety.
For the last several days, Isabel and her daughter had been living in one of the hundreds of tents in Matamoros, where as many as 2,000 migrants sleep in a camp with limited access to food, water, and medical care, and where some people sleep near toilets overflowing with feces. Isabel says they shared their tent with another woman and her two children.
A letter from Global Response Management says the girl is "at great risk of possible systemic infection."
She "should not be living in the harsh environment of a refugee camp," the letter reads.
Border agents can exempt migrants from "vulnerable populations," which has in practice included people with serious illnesses. But immigration lawyers say agents have wrongly excluded many sick people, leaving them to wait for months in the shelters or squalid encampments that have cropped up next to the border. In one case this year, border agents took a woman who was 8 1/2 months pregnant to a hospital in the U.S., where she was given an injection to stop premature contractions. They then sent her back to Mexico.
Since their expulsion under the "Remain" program, Isabel and her daughter had asked the border guards at the main bridge connecting Brownsville and Matamoros three times to exempt them from the program. They had their first court hearing Monday and were sent back to Mexico, and told to return again in March.
That changed on Tuesday, when a CBP official contacted one of the family's attorneys to say they would get another chance at the bridge. Isabel and her daughter were taken inside CBP's office on the U.S. side and eventually released to their attorneys, who took them to a hotel.
"It shouldn't take literally a village of lawyers and advocates four attempts over the course of a week and several hours of waiting for the U.S. to take responsibility and fix what occurred because of the conditions in CBP detention," said Kim Hunter, a lawyer with the advocacy group Project Corazon.
As her daughter watched "A Charlie Brown Christmas" on a hotel television, Isabel wept with joy and thanked her lawyers.
"I don't have any words for the support they gave me and my daughter," she said.