The family of a teenager who came close to being deported on her own are to be sent back to Mauritius along with the 19-year-old after losing their appeal, it emerged on Tuesday.

The Bageerathi family's case came to light last week when it emerged that the eldest daughter, Yashika, was due to be separated from her family and deported alone because she was considered an adult.

She was given what appeared to be a last-minute reprieve on Tuesday afternoon when it was claimed that British Airways had refused to put her on its flight and she was returned to a detention centre. But the family's celebrations were short-lived, as later the same day it was announced that the whole family was to be sent back to Mauritius.

Solicitors working on Yashika's case were told that it had been rejoined with that of the rest of her family, and that the appeal against their deportation had been rejected. On Tuesday evening, the news was broken to teachers and friends of two of the family's three children at the Oasis Academy Hadley, in north London, who have led a campaign to block the deportation supported by more than 100,000 people.

Headteacher Lynne Dawes said she thought the move was an attempt to dismiss their argument that deporting Yashika would split up her family. "I'm not proud of my country treating people in this way," she said. "Her mother is not coping, she's really struggling and is very tearful."

The family, including Yashika's mother Sowbhagyawatee, 38, sister Shaivya, 16 and brother Cherish, 11, will now be deported.

Lee Pedder, 18, a friend of Yashika, said: "Our legal team are pushing them and we will continue to as well. If her entire family is going to be deported, we will support them all. This is a massively cynical tactic to try and shut up democratic oversight."

Estyhia Tangeli, 18, said the decision to deport both girls from the school, and the rest of the family, was disgraceful. She said: "It makes them look worse as they will lose two valuable members of society; her sister is predicted As and A*s in her GCSEs she's about to sit."

Another friend, Shantelle Creed, 17, said: "We're showing just how passionate and engaged we are and they're backing us into a corner. We won't stop."

Yashika's case also attracted support in Westminster. Conservative MP David Burrowes made a plea to the Home Office on her behalf. He said that British Airways had refused to deport the teenager on Tuesday afternoon, leading to her being sent back to Yarl's Wood detention centre, in Bedfordshire.

The family came to the UK in 2012, fleeing violent threats from a family member.

The shadow immigration minister, David Hanson MP, called at the weekend for the family's case to be reconsidered. A student at Yashika's school said that he phoned the office of Hanson's opposite number, the Conservative immigration minister James Brokenshire, and was told they were "supportive" of the campaign to keep Yashika in the country.

A Home Office spokesman said: "The UK has a proud history of granting asylum to those who need it and we consider every application on its individual merits. We do not routinely comment on individual cases."

British Airways refused to comment, citing data protection laws. James Brokenshire MP did not respond to repeated requests for comment.