Hi Ohio. Several thoughts come to mind. Some people have neurological reactions to computer screens. Mostly it's computer games though...it tangles up the brain somehow and can cause seizures....some kind of epilepsy I think. Does she spend a lot of time in front of the computer? Perhaps you should suggest that she limit the time she spends, or takes breaks away from the screen for awhile. Sometimes I know that I have had migrane headaches triggered by too much time on the computer.
Secondly, due to her age, she may be expeirencing some hormone fluctuations which could possibly cause the sweating and shakes. Maybe jot down when, during her month, these things occur.
Given that she is having all kinds of symptoms that are causing you both concern, I would STRONGLY recommend that you get a calendar book and have her write down her symptoms for a month or so every time they occur. If there is some kind of a detectable pattern, then she could help herself overcome them with a doctor's help.
It may be that due to the scary news about her heart that she is having panic attacks and they are manifesting themselves in these weird ways.
These are very real things for her and it is absolutley wonderful that you are honoring her by asking us and, hopefully still, her doctors for help. By writing everything down when it happens, you will have clearer information to give your doctor. Things like, what had she just eaten when she got all shakey. How long had she been on the computer? was she using the IM and having lots of words bouncing back and forth on the screen, or was she just reading some text for homework? Is she in the middle of her cycle? Does she also get a headache? that kind of thing.
Hope this helps. Keep asking!!
Marguerite