A mountain lion makes a "throaty sound" like gravel in a bucket, or like the sound of a person walking in deep gravel. It means she is confused - like "what is this new boulder in my territory and why does it smell of a strange animal?" At that point yelling, waving arms etc, just going ballistic, will scare her off. I have first hand experience with this. Now if she growls, its more of a challenge and immediate action is required, scream back at her. Another technique used by some friends is to get lower in your sleeping bag and cover your head and cower.
Jim