The 47-year-old activist has always raised 12-year-old Beatrice, her child with ex-husband Beatle star Paul McCartney, on an animal product-free diet, reported Femalefirst.
Heather said: "Her whole life she's been vegan. And unlike the kids at school she doesn't get sick, she doesn't get colds.
"They just don't understand it, the same parents she has been at school with for seven years will ask me what to feed the kids, whereas before they frowned upon the fact that I was bringing up a child that's completely vegan.