For more than nine months, María, 23, has been waiting in an immigration detention center in Arizona hoping to reunite with the six-year-old niece she raised as a daughter. When the two asked for asylum at the border last March because they feared for their lives in Guatemala, border officials detained María in the Eloy detention center and sent the girl to foster care in New York, 2,400 miles away.

The Guardian first reported on the ongoing separation of this family in October. As the story spread, lawmakers and more than 200 clergy asked US Immigration and Customs Enforcement (Ice) to grant María parole so she can leave detention and reunite with the girl. A woman in New York volunteered to house them both while María awaits a decision on her appeal for asylum.

But despite that public support, Ice denied María’s application for parole in mid-December.

Parole was once the norm for arriving asylum seekers, but in recent years approvals have become increasingly rare. On a standardized form, Ice officers indicated María failed to prove she was “not a flight risk” or that her “continued detention was not in the public interest”.

A group of supporters gathered at the Arizona state capitol to call on Ice to grant María’s parole. Photograph: Jude Joffe-Block/The Guardian

María said the denial was “depressing” because it prolongs her separation from the child. She has regular phone calls with her niece, who says she doesn’t want to be apart any more. “But I tell her she has to be patient, wait a little bit longer. Just like I’m doing it myself from here,” María said in Spanish during a phone call from detention on Thursday.

“Why does Ice get to say what the public interest is?” said Suzannah Maclay, one of María’s pro bono attorneys. “It’s very clear what the public is interested in here. It’s helping these people and getting them back together.”

An Ice spokeswoman emailed a statement reciting the facts of María’s case but did not answer why the agency denied parole.

Six years ago, a gang in rural Guatemala murdered María’s last living relatives except her niece, who was a baby. María raised the child and is the only mother the girl has known. They fled toward the United States last Christmas after the gang murdered María’s partner and tried to shoot her.

María’s case stands out because of the dozens of people who have tried to help.

The support began when María and her niece first arrived at a shelter on the Mexican border and met American volunteers. They helped obtain copies of official birth and death certificates that prove her relatives were violently murdered and her relationship to the girl.

At that time, a federal judge had halted the Trump administration’s policy of separating most families at the border nearly nine months earlier. Yet a US law aimed at protecting child migrants from traffickers requires border officials to separate arriving children from adults who cannot prove they are the child’s parents or legal guardians. Officials did not accept the documents María showed as proof of legal guardianship.

Once María was detained, some of those volunteers from the shelter found her pro bono attorneys and located her niece in New York.

“She would have totally lost track of her niece,” said Maclay. “But it was because the public stepped up and kept track of where the little girl went that they’re even in contact right now.”

Arizona state representative Kelli Butler, center, calls on Ice to grant María’s parole on 19 December. Photograph: Jude Joffe-Block/The Guardian

María’s supporters are calling on Ice to reverse course and grant her parole. A small crowd of state legislators, clergy and activists gathered on the state capitol on Thursday holding signs that read “Uncage & Reunite” and “Call ICE” with the agency’s local phone number.

The Rev James Pennington of First Congregational United Church of Christ in Phoenix said by keeping the family apart, Ice is “causing further pain, trauma, mental, physical, spiritual health issues that will extend far beyond just this moment in time”.

He added, “It is beyond cruel especially at this time of Christmas.”

Anita, the New York woman who has volunteered to house María and her niece, said she has already sent them photos of the family. “I told her we’re all waiting for her,” said Anita, who asked for her last name to be withheld to protect María’s safety if she is released.

“We’re so anxious to have a good resolution for this case, but at the same time painfully aware that there are so many other people that don’t have this kind of support,” she said.

When the Guardian first wrote about María, she asked to be called Alexa for fear of reprisal. But she has since chosen to use her real first name in the press as a growing number of supporters are calling on Ice to release her.

After a federal judge in 2018 ordered most family separations to end, attorneys have been scrambling to reunite families. There are currently about 5,500 known cases of children separated from parents during the Trump administration. But no one has tracked how many children have been split from non-parent relatives, nor is there a formal mechanism for those families to reunify.

The logistics of how and when María will see her niece again if she is not paroled are unclear. María’s asylum appeal could take up to two years. Sean Wellock, another pro bono attorney representing her, said if María were to lose her appeal, the government would be under no obligation to coordinate a reunion in Guatemala with her niece if they are deported separately.

The girl could lag behind María by days, weeks or months.

Christie Turner-Herbas, an attorney specializing in reunifying migrant families at Kids in Need of Defense, said when a child is deported alone, US government agencies do not always communicate clearly about the child’s travel.

“There have been complications like a child is leaving and we never get any notice,” Turner-Herbas said. “And then we find out, you know, get a panicked call from the family saying that they heard the child is coming in, but they’re not able to get [to the airport] in time.”

María says her days in detention are monotonous until someone visits or she receives a letter. While she says the government has denied all her requests, she still doesn’t “feel abandoned”.

“I have the support of lots of people,” she said. “I’m not alone”.