If we are to assume that she has no issues with her lungs, a "normal ejection fraction" does not rule out heart related causes of shortness of breath. One of the often missed or under recognized but very common causes of shortness of breath is what is referred to as diastolic dysfunction. Putting it simply, how "complaint" is the heart or how "stiff" has the heart become over time. As we age and with other risk factors, the heart becomes less complaint and it is the commonest cause of shortness of breath and cause of heart failure what we now refer to as Heart Failure With Preserved Ejection Fraction (HFPEF).
Secondly, severe coronary artery disease can often present just as shortness of breath with exertion in the presence of normal ejection fraction (although over time the ejection fraction will slowly decline).