She made her first significant mountain ascent in 1892 when she climbed the Aiguille des Grands Charmoz in the Mont Blanc massif with Albert F. Mummery and his wife Mary. With their success, Bristow and Mary Mummery became the first women to climb the mountain. In 1893, Bristow climbed the Aiguille du Grépon—the ascent for which she was best known. This was the second-ever traverse of the Grépon, which had first been climbed by Albert Mummery two years earlier. The same year, she successfully climbed the Aiguille du Dru, the Zinalrothorn and the Matterhorn. She was known for climbing without local guides and for occasionally leading her climbing parties' ascents. Bristow's guideless ascent of the Grépon inspired Mummery to write: "All mountains appear doomed to pass through three stages: An inaccessible peak, the hardest climb in the Alps, an easy day for a lady."
It was noted that Bristow caused scandal amongst her acquaintances by choosing to share tents with men. Some have speculated that Mary Mummery later forbade her husband from climbing with Bristow, since Bristow did not accompany him on any of his 1894 expeditions, and there are no records of Bristow continuing her climbing career following his death on Nanga Parbat in 1895.
- England & Wales, Civil Registration Birth Index, 1837-1915
- 1871 England Census
- Oliver, Hilary (4 September 2013). "Historical Badass: Climber Lily Bristow". Adventure Journal. Retrieved 29 March 2014.
- Mazel, David (1994). "A real snorker". Mountaineering Women: Stories by Early Climbers. Texas A&M University Press. pp. 78–83.
- Jones, Susanna (27 March 2012). "For the female mountaineering pioneers, it was an uphill struggle". The Guardian. Retrieved 29 March 2014.
- Willett, Maxine (6 August 2006). "Entity: Bristow, Lily (fl.1883–1894)". Mountain Heritage Trust. Retrieved 29 March 2014.
- Sparks, Elisa Kay. "'The Evening under Lamplight … with the Photograph Album': To the Lighthouse as a Family Scrapbook". In Burrells, Anna (ed.). Woolfian Boundaries: Selected Papers from the Sixteenth Annual International Conference on Virginia Woolf. Clemson University Digital. pp. 164–171. Retrieved 29 March 2014.