in a basic nut shell it means the heart is beating to fast to let the pumping chamber of the heart to completely fill with blood to make it a good pump. There for it is making her fill terrible. There are medications that can treat this. Yes it would freak anyone out and she has just rights to feel anxious, but anxiety
does make it worse. The best thing you can do is help her through it and let her know how important it is to follow directions of medications provided by the doctor. stay away from caffeine or any stimulants for that matter. The electrical stuff is the brain of the system but the reason she is symptomatic with the SVT
is, well think of a turkey baster if you don't squeeze it slow and fully it doesn't pump correct does it. now try for one minute to squeeze it all the way 60 times in own minute now try 300 in one minute. how much liquid were you able to displace. Get the idea now. To fast to be useful. In the long run this will also cause the heart muscle to enlarge and make even less of a good pump.
The quick tricks listed above are to invoke a vagal response, have her grunt like she needs to have a poop, same thing,