Arnot was raised just outside Glacier National Park in Whitefish, Montana. After college, she began living out of her car to save money and climb mountains. She first climbed Mount Rainier in 2001 and called it a watershed moment. She began teaching wilderness medicine in 2002 and began guiding on Mount Rainier with Rainier Mountaineering, Inc. in 2004. By 2006 she was a lead guide.