Not often that animals around here (Colorado) attack humans. We only have two predators usually capable of doing this, Black Bears and Cougars. Neither frequently attack people unless you startle them and they are acting protective. Black Bear attacks typically happen in the fall as they fatten up for winter. It is possible that she was attacked by a cougar, but usually remains are easy to find and the division of wildlife is really good at tracking aggressive cougars. It's possible but IMO unlikely.
Didn't they say they didn't even search until days later when Eli got to Crestone.If it was an animal its possible all the evidence would be gone by then. Although I highly doubt this is the case.
List of fatal mountain lion attacks in the US https://en.wikipedia.org/wiki/List_of_fatal_cougar_attacks_in_North_America#2010s List of fatal Black Bear attacks in the US https://en.wikipedia.org/wiki/List_of_fatal_bear_attacks_in_North_America As you can see, very low numbers.
Every animal within a mile of the drum circle would have taken off when the drumming started. Unless she was still wounding around in the woods the next day?
There would of likely been signs of animal perdition likely if that was the case.