Each person is psychologically unique.
Alex Honnold's Brain and his fear response have been studied extensively and yet the conclusions are still conjectural. The link is quite and interesting read. I don't think you can directly compare Honnold's climbing directly with Gillet's solo paddle to Hawaii. Both are/were, obviously motivated to do things that the rest of us either find insane, or unbelievably bold. Only they know why they do what they do.
When I watched "Free Solo", I found myself wanting to look away sometimes when the moves got really thin. I noticed one of his friends who was filming from the ground, appear to do the same thing in the movie. The fact that the film maker and I were both climbers, meant, at least for me, that I knew exactly how tenuous the moves were and could not comprehend how Alex could possibly calm the fear, even the slightest doubt or quiver, which would have resulted in falling.
Many of us have also likely experienced reactions from friends, family and acquaintances who cannot understand why we seek the adventures we do. The more extreme the trip or adventure, the more intense the sense of wonder or disbelief from the average person. My most intense experience of this was at the funeral of a climbing partner who died in his late 20's, in a mountaineering accident. Perhaps I was over reacting, but many of his close family and family friends seemed to me to be observably upset and confused by the presence of his climbing friends at the funeral. His best friend, a climber, had been asked to say a few words about Bob. During his eulogy, he said "Bob died doing what he loved", which was true. But there was a visible body language and expression reaction from some of his family, his mother and sisters in particular, when they heard those words. They were meant to comfort, but only someone who understood the drive to climb would find them so. For his family, they simply reinforced the insanity of the risk taking for them.
At this point in the thread, we are far off the topic when we are discussing the extreme end of adventure sports. The young lady in question is not contemplating anything so extreme. Merely taking a step into the world of solo adventure for her own reasons. I personally think there are various reasons for going into the wilderness and testing oneself, so to speak. For some it is thrill seeking, for others, seeking solitude, communing with nature, etc. Suffice it to say, that for those who do solo trips, or even lengthy high risk trips with others, there is a psychological reward of some sort in doing so. Each of us has our own reasons and our own standards for facing risk and methods for dealing with fear. Preparation and a clear focus on what you are planning and a realistic attitude to any risk you think you might face are required.
For the young woman for whom advice was originally sought on this thread, from the description of her, she has a strong desire. The fact that she asked a mentor for advice would seem to be a sign of a good attitude about preparing for solo paddling as well. If she did not have a good attitude, she would not have asked. The rest will come with time, experience and desire. The first step, the first solo adventure, is the hardest. That will be the test to see if her dream is just a dream, or becomes a manner of being.
The best advice on this thread in my opinion is from the person most qualified to give it:
"Not being afraid to turn back; and not being too hard on one’s self after turning back"
Some of the worst decisions I have ever made were allowing myself, or someone else to goad me into taking a risk that I was not completely comfortable with. Listen to your inner voice and your instincts. Your greatest safety asset is your gut.
Lots of sound advice and experience on this forum for her to learn from.
Cheers, Rick