The 23-year-old, who is firmly against animal cruelty, cancelled her public appearance at the department store in London because it stocked animal fur.
Harrods said it was told she cancelled "due to a scheduling clash".
Lewis, was recently voted the UK's sexiest vegetarian.
"I'm totally against animal cruelty," she said at the time. "I don't have clothes, shoes or bags made from any animal products."