Hello.
If you have questions about heart function, I suggest you ask them in the heart disease expert forum at:
http://www.medhelp.org/forum_disclaimers/show/114
I can't comment on your friend's health. Obviously, she has a heart condition that has caused her physician some concern. Most people don't realize that the heart rate increases dramatically during sexual arousal. For this reason, if there is any weakness or disease or other condition in the heart, such increase may be dangerous.