Hi Gabby,
Same as Tom recommended. Also, some links.
http://www.nhs.uk/conditions/Supraventricular-tachycardia/Pages/Introduction.aspx
https://en.m.wikipedia.org/wiki/Supraventricular_tachycardia
But there are other forms of Tachycardia that a Doctor must determine if it could be a problem, and a Monitoring Device (a Holter records the heart signals for 24 hours or more, an Event Monitor may be worn for weeks or until they electronically capture the heart signal that is causing the symptoms) is usually used so that a Doctor can see what is really occurring.
Many of these rhythms are not considered dangerous, but a doctor needs to make that determination. More sleep, avoiding caffeine, cigarettes, chocolate, recreational drugs, diet and some cold medications, etc. may help to prevent these rhythms from happening.
This is not a doctor's forum, but for those of us who have heart issues. Please have your friend Google "Supraventricular Tachycardia symptoms" and see if they match what she is experiencing. Of course, she should see a physician, but this will give her something to compare her symptoms to.