We unfortunately can't tell you online. She needs to see a doctor and sometimes repeat visits have to happen before we get to the bottom of things. I would first ask if she has a lot of anxiety. Anxiety and panic may be a cause. I would also ask if she is eating and drinking enough water. Being under nourished or under hydrated can cause issues. Simple hormone imbalances could also be a cause. If the ekgs are showing disturbance then push to get further testing done. It can be a time consuming process to get to the bottom of things but as patients we need to be persistent and keep at the doctors to get things sorted out. take care and hope your sister feels better soon.