Sad that this woman was killed and condolences to her family and friends.
I have lived in CO for over 40 years and have run and hiked many thousands of miles in wild natural areas. I have been lucky enough to see 3 lions while out running and 1 while hiking, have seen many lion tracks and have come upon 3 lion kills. I am sure many lions have seen and stalked me.
There are lions just about everywhere in CO and there is always a very slim risk that you will be attacked by one. You can do things to minimize that risk but nothing is going to help you when a healthy adult lion gets a good chance to kill you. They are incredibly agile, strong and smart predators. They normally stalk and attack from behind aiming to jump onto and hit the back of your neck. If that blow does not severe your spine instantly they will clamp down on your neck severing your spine and/or quickly suffocating you. Likely you will never see the lion and will be dead before you know what happened.
Lions put themselves at great risk when attacking big prey like elk, deer or even people. They are really smart and will stalk but avoid attacking unless the conditions are right.
Sometimes inexperienced/juvenile lions will attack people, as will weak/sick/malnourished/desperate lions. And rarely healthy adult lions will misjudge or mess up a little while attacking.When those types of attacks occur you likely will not die instantly and have a chance to fight back and live. Normally you will not have a chance to use things like bear spray, spears, knives or guns when you are fighting for your life with a lion on your neck.
The odds of seeing a lion while you are out in the wild are slim, and it is even rarer to be attacked by a lion and rarer still to be killed by one. You have an exponentially much much greater chance of being injured/killed while traveling to a trailhead or wild area than encountering a lion while there.
The best we can hope for is this woman was truly enjoying her hike and died instantly while doing something she loved.