Miss Dean was born with her left forearm missing
The mother of a disabled woman suing clothing firm Abercrombie & Fitch over discrimination claims said her daughter had suffered "devastating damage".
Riam Dean, 22, who has a prosthetic arm, claims she was made to work in the stockroom of the flagship Savile Row store for not fitting their image.
Her mother May Dean, 50, said her daughter refused to leave the house all summer after the incident on 4 July.
A manager at the store insisted Abercrombie values inclusiveness.
On Wednesday Miss Dean, a student at Queen Mary University of London, who was born with her left forearm missing, said she had been "taunted" and "goaded" by Abercrombie manager Maria Barbera.
Ms Barbera allegedly told Miss Dean she could only return to the shop floor if she removed a cardigan that the student used to cover her prosthetic arm.
Her mother told the tribunal on Thursday that the encounter had left Miss Dean "distraught".
Mrs Dean said: "I did not want her to suffer any further distress, so told her to leave immediately.
"There was no reason for her to put up with this kind of humiliation."
Mrs Dean continued: "Riam said the manager was sure she would not want to show the prosthetic hand - and would therefore be bullied and embarrassed into accepting a position in the stock room.
'Remained in house'
"I don't know whether she did it out of ignorance or spite - whichever it was the damage was devastating."
She added: "We had never seen Riam withdraw the way she did after this incident, refusing to leave the house the entire summer holiday."
Benjamin Fogel, a senior manager at the store, told the tribunal: "Diversity and inclusion is taken seriously at Abercrombie.
"I was disappointed that Riam did not feel able to take up my invitation to resolve the issue but instead tendered her resignation.
"I would have much preferred to listen to Riam's concerns and to attempt to address these for her."