It's a scary feeling! I bet your friend tries to stay away from chocolate too since it has caffeine.
It's surprising the things she avoids now. A few years ago my wife and I were at a party with her and her husband (and a load of other people) and she suddenly had to leave. At the time we didn't know about her issue so thought it was something unrelated, but it turned out she had gone to the ER with her pulse out of control. I'm not sure what she had had that triggered it, but it highlighted just how serious the situation was.
When I'm exercising hard I can push my pulse over 180. If it goes over 185-190 I just can't sustain the intensity for more than a very short time. I can only imagine what it's like to have that kind of heart rate without exercising, and without the option to ease off and let it drop.