Gamu’s mum Nokuthula, 38, left Zimbabwe eight years ago and settled in Tillicoultry, Clackmannanshire, with her daughter and two sons Milton, 12, and Marty, 10.
She was in Scotland under a work permit visa, which also covers her children as her dependants.
However, when the family recently applied for an extension, they were stunned when it was rejected.
Worried Nokutula is set to meet immigration officials during the week to discuss the new application.
The family's lawyer Frances Farrell, of Glasgow-based Peter G. Farrell, said: "Discussions are ongoing and we hope the situation can be resolved."
Gamu wowed the audience and judges at the Glasgow auditions earlier this year with her rendition of Katrina and the Waves' hit Walking on Sunshine.
The teenager was just three when her dad died in Zimbabwe and her mum struggled financially to bring up her children.
Nokutula eventually made the heartbreaking decision to leave them and fly to Britain to study.
Gamu and her brothers stayed with family members in Harare while her mum came to Scotland to study for a degree at Stirling University.
Three years later, the familywere reunited in Scotland and Gamu told the X Factor audition audience at Glasgow's SECC she just wanted to give something back to her mum.
The judges all heaped her with praise after her song, with Cowell describing the teenager as "really talented".
Gamu's audition has already had more than 1.5 million hits on YouTube - more than any other hopeful on the show - and she dedicated her success to the people of Scotland.
She said: "Without this country's help, it wouldn't have been possible."
She added: "I regard myself as a Scottish contestant, because this country has been so good to me.
"I have loads of great friends and loads of good people around me. It has been great."