Nigeria’s first lady has joined the chorus of voices condemning the killing of a student abducted along with her five sisters, calling it a “devastating loss”.

Nabeeha Al-Kadriyar, 21, was “super-bright, smart and kind”, her cousin Asiya Adamu told the BBC on Monday.

Nabeeha also loved to write poetry and read books by the American author Jodi Picoult – and she was days away from graduating with a science degree from Ahmadu Bello University.

“On the day the kidnapping happened, I asked Nabeeha if we were going to the [graduation ceremony] together, and she said yes,” recalls Ms Adamu. It was the last time she saw her alive.

That evening, on 2 January, Nabeeha was abducted along with her father and sisters from their home in the outskirts of the capital, Abuja.

Nigerian police have not confirmed what happened next. Witnesses say Nabeeha’s uncle ran to find help but was ambushed and killed, as were three police officers. It is not known why the family was targeted.

The kidnappers demanded to be paid a huge sum of cash by 12 January, and when they did not get it they killed Nabeeha as a warning, according to a member of the family who spoke to the BBC on condition of anonymity.

Nabeeha’s kidnappers handed over her body and, in accordance with Islamic rites, she was swiftly buried by her family on Saturday.