The charity said the nine-year-old was planning to celebrate hitting the £100,000 mark by holding a small porridge party with her family and tasting likuni phala, the nutritious porridge-like dish which Mary's Meals feeds to children at its largest project in Malawi in order to attract them to the classroom.
It costs Mary's Meals about £10.70 to feed a hungry child for an entire school year.
Magnus MacFarlane-Barrow, founder and chief executive of Mary's Meals, said he was humbled by Martha and her friends.
He added: "This is incredible and I can't thank Martha and her supporters enough for everything they have done.
"As a result of their amazing beautiful acts of kindness, the lives of thousands of the world's poorest children will be transformed."