Her brother, James Middleton, accompanied her during the mountain climbs and shared his reflections on Instagram.
"Incredibly proud," he wrote.
He described the joint trek as a meaningful milestone.
"Honour," he wrote.
He recalled past conversations they shared during her hospitalization.
"Two years ago, I told you we'd climb this mountain together," he said.
He noted the mental and physical benefits of spending time in natural environments.
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"We talked about climbing mountains while you were in hospital, and about the incredible healing power that nature can have for both the body and the mind," he said.
He commended her endurance and roles within the family.
"Seeing how far you've come is nothing short of inspiring.
Your strength, resilience, and determination, all while being the most amazing mother, wife, daughter, and sister, inspire me and so many others every single day," he said.
During her ascent of Ben Nevis, the princess encountered an 11-year-old wheelchair user named Ted, who was raising money for Molly Olly’s Wishes.
She later made a donation to his JustGiving page.
"One of the real highlights of the Three Peaks Challenge was meeting inspiring people like you along the way.
Huge congratulations to Ted, Pete and the entire team for raising money for such a wonderful cause," read a message left by the princess.
The fundraising page, established by Ted's father Pete Haslam, has raised more than £11,000.
"Ted is a wheelchair user — but that’s never been the thing that defines him. Determination does.
