How did princess of wales' help ban land mines?

Answer 1

She didn't. There are land mines all over the world. She talked about banning land mines. She made it one of her favorite subjects to talk about. Princess Diana tried to ban land mines, but, she did not succeed in her cause.

She is believed to have influenced the signing, though only after her death, of the Ottawa Treaty, which created an international ban on the use of anti-personnel landmines(36). Introducing the second reading of the landmines bill 1998 to the British House of Commons the foreign secretary, Robin Cook, paid tribute to Diana's work on landmines.
She travelled to some of the evacuated war zones, and went out on mine-clearing patrols organised by the charity HALO.

She was a very popular figurehead, and drew world attention to the mine-clearing operations.