OK...here is a subject I CAN speak about with some knowlege...
Heart Palpitations are almost always various forms of RAF...or "Rapid Atrial Fibrillation" They are only felt in the chest as "flutterings" and not pain. Episodes of RAF can be associated with feelings of tiredness and lethargy, these usually pass within 24 hours of the episode ceasing, or as they say "reverting" back to a normal Sinus Heart Rythm.
In themselves RAF episodes are not in any way life threatening, they dont know what causes it , except that it is likely due to some genetic imbalance in the electrical wiring of your ticker.
Doctors are reluctant to prescribe drugs for this complaint as they usually fix themselves within 4 hours of an episode. The majot risk is an RAF episode that goes on for more than 24 hours...there is a certain amount of turbulence in the blood flow in the heart during these episodes, and prolongued turbulence can, in rare instances result in a blood clot forming which IS obviously life threatening.
I (and about 75% of the population over 50 years old) have had RAF for nearly 30 years. It affect Men 4 times more than Women, but Women do get it also.
To manage this problem, it is essential to lead an active life and get fit, exercise HELPS keep the episodes away, excercise while in RAF cannot trigger a heart attack, The BIg Bad Fibrillation to be a ware (and scared of) is Ventricular Fibrillation...if you dont get help with this beast, you are dead within 5 minutes !!!! But you will surely know if you are getting V Fib...you will be in severe agony and you WILL be having a heart attack !!!
The Atrium chamber in the heart is where the "pull" of deoxegenated blood happens, whilst the Ventricular chamber manages the "Push" or pumping. Even though the "pull" cycle is disturbed during RAF, the Ventrical "Pump" has enough power to keep going perfectly adequately during this time.
Normally, RAF is not a reason for any further Medical downgrades...such as life insurance, Pilots License or whatever.
What triggers an episode ??/...not sure, it can be stress, tiredness, panic attack, overthinking....many different reasons. Most affected people have their own way of dealing with it...for me...sex helps (hahaha) and so does 30 minutes in the Gym !!!!....I will leave you to decide which one I prefer
Above all, please dont get scared that this is MAJOR heart issues. If it is RAF, you have very little to worry about. But I cannot say if this is her condition, only a "proper" Medical will establish this or some other underlying issue.