Hi
Hi agree with the above posts. May I add just one aspect to the answers. From a psycho-neurological point of view, we believe there is one particular part of the brain involved with fear. This part does not deal with logic or rational thinking. It can only deal with associations. So during that particular flight, your friend's brain made a specific association between fright and flying/turbulence and it does not matter how much logic she uses, that part can't "listen" (this part is in the limbic system and involves the amygdala, hipocampus etc).
So, to treat this porblem, specifically when the association is very intense, she first needs to do some form of desensitization. This is where hypnosis, NLP, EMDR and other psychological procedures can help. But even if you don't use these procedures and she is prepared to slowly confront her fear, then the brain will automatically adjust and go through a natural process of "desensitization". It might just take a bit longer.
But by all means tell her it can be overcome and is a very normal response. Her brain works fine!!
Good luck!
FS