Dorothy Howell Rodham, who passed away in 2011, helped inspire Clinton's passion for public service after overcoming an abusive childhood in Chicago.
"Mom helped Chelsea navigate the unique challenges of growing up in the public eye and, when she was ready, encouraged her to pursue her passion for service and philanthropy," she writes in the excerpt published in Vogue from her upcoming book. "Even in her 90s, Mom never lost her commitment to social justice, which did so much to mold and inspire me when I was growing up. I loved that she was able to do the same for Chelsea."
Clinton also writes in the excerpt about the blessings and challenges of taking care of an aging parent.
"Mom was a fighter her entire life, but it was finally time to let go," she writes. "I sat by her bedside and held her hand one last time. No one had a bigger influence on my life or did more to shape the person I became."