The former model, who started lobbying against land-mines when she lost her leg in a motorcycle accident in 1993, is convinced she would have been good friends with Linda, who died from breast cancer in 1998.
Mills McCartney says, "She was a fantastic animal-rights campaigner.
"She was the kind of person I would admire much more than, say, a Beatle.
"Yes, they wrote some good songs and got rich, but even while they were doing it sometimes they would admit it was for a swimming pool or to build a bigger house.
"Linda was not afraid to speak out for what she believed in."