The 19-year-old took the stage at the Scribbler's Picnic in Stirling, an annual festival in aid of cancer charities.
The singer, who is currently fighting deportation, said the performance was "a thank you to the community for their support" - and revealed the event was especially poignant for her as her own father, Thompson, died from lung cancer when she was a young girl in Zimbabwe.
Gamu, accompanied only by a guitarist, performed four songs on the festival's main stage, including Make You Feel My Love, the Adele hit that won her an army of fans on the X Factor, and one of her own compositions.
She said: "This is the first time most people in Scotland have been able to see me since X Factor, and … it's a chance to say thanks to a lot of people who have supported me in the last year."
The teenager and her family - mother Nokuthula Ngazana and brothers Milton, 11, and Marty, nine - have since been battling to remain in Scotland.
Ms Ngazana initially had her application for renewal of her visa rejected by the Home Office. After various hearings and a campaign by Scots supporting the family's bid to stay in Scotland, they finally won the right to stay in April. However, the Home Office appealed the decision, and the family is now awaiting the outcome of that appeal.