Fatou Cham, 32, came to the UK from Gambia, West Africa, in 1998 on a student visa but stayed after it expired in 2001.
Miss Cham, who works at the Tesco store, in Beckton, east London, was chosen from hundreds of hopefuls to model the Florence and Fred clothing range for an ad campaign used in women's magazines.
Next to a picture of Miss Cham modelling a blue dress and heels were the words: "Designed by F&F. Priced by Tesco. Modelled by Fatou, checkout number 6, Tesco, east London."
Immigration officers questioned her at her home in East Ham, east London, on Monday.
The mother-of-three was unavailable for comment when contacted by Sky News Online.
She was quoted in the Sunday Mirror as saying: ""I came here for a better life and never set out to deceive anyone.
"I just want to stay here with my family and be happy."
She said she had been excited to be chosen for the Tesco campaign and had hoped it would bring her other opportunities.
"Now it has all gone horribly wrong," she added.
Her solicitor Jamil Trawally told the paper: "I am sure she was brought to the attention of the police because of the Tesco campaign."
Miss Cham initially came to the UK to study banking, economics and finance at London Metropolitan University.
Her mother and eldest child were allowed to join her in the UK in 2000. Her two other children were born in Britain.
Miss Cham applied to stay in the UK when her student visa ran out but was refused permission.
A further application in January this year was also turned down and she has appealed to the High Court.
When Miss Cham joined Tesco in 2002, overseas citizens just needed a national insurance number to work in the UK.
But since 2004 they have been required to have a valid work visa, although this did not apply to those already in employment.
A Tesco spokeswoman said: "As soon as we were made aware of this issue by the UK Border Agency we co-operated fully with the investigation.
"We carried out all the checks required by law and the authorities have confirmed that they are satisfied that we followed the correct procedures."
A UK Border Agency spokesman said: "The UK Border Agency expects people with no right to be here to return home voluntarily, if people do not we will remove them."
...or did she say "Every Lidl helps!"?
©TITVS-ADVXAS XXVII-IX-MMIXtitvs advxas