In the video, she said she was hunting on Nov 1. with her dad in the woods near Gunnison, Colorado.
McKenzie said she and her dad were split up in different areas of the woods when she looked up to see a "majestic mountain lion standing right in front of me."
She said the animal was probably about 16 yards in front of her at this point.
"It was close enough I could see its eyes were blue-green and it was just staring at me," McKenzie said. "It was not scared. It was not startled. Unlike me."
She tried to scare the cat off, but it was not scared. In the end she had to shoot it, as it attacked.
She described the encounter as "the craziest moment of her life."
McKenzie reported what happened to the state wildlife officials and showed them the video.
She said the officers told her it was a clear case of self-defense and that she did the right thing.
McKenzie said the mountain lion did die.
"I'm very sad about that," she said. "I wanted it to keep living. That's why I tried so hard to scare it away. I didn't want to shoot it. I mean, it was the most beautiful creature I have ever seen up close like that."
You can see the video at this link, or below. You want to see the video if you have the 10 minutes. The video she recorded on her phone, followed by a few minutes of commentary after-the-fact.
Self-defense is a Human-right.