She needs to realize that stress is not just one big thing and that there are many different types of stress.
Here we can see a difference between physical stress, and mental stress.
Physical stress being the stress that the body puts on itself to be able to perform a task to it's best ability when it's required. Whether that be writing your name, or pulling yourself up from the edge of a cliff.
Then there's mental stress which works on your body's ability to perform cognitive tasks.
When you are worried or anxious about something, it creates a sense of resistance in the body and mind. When you are more accepting of the stress or the feeling, you are able to free yourself from that resistance and all of the mental work that goes into the resistance, which allows your mind to have more capacity to focus.
The physical stress remains because your body is still pushing itself to perform a task under pressure.
Put all of this together, and you get the same result, except it makes much more sense to not think about stress as just one single thing.
That being said, being chronically stressed is probably still unhealthy for body and mind.