hello, Usually supraventricular tachycardia is usually episodic in nature and will not cause persistent shortness of breath. First thing is that, the type of supraventricular tachycardia should be determined. So get one ecg done and upload it or show it to local doctor. If she is having persistent type of supraventricular tachycardia like atrial fibrillation then only it can cause this type of symptoms. For this rate control drugs like metoprolol etc are available and control the symptoms very well. Secondly we need to find for another cause, for that she ll need echo, hemoglobin testing. In general, she should have salt and fluid including water tea milk coffee etc restriction to minimum. Very good medicine are available so you either upload her reports or visit local doctor. She ll medicine like metoprolol, torsemide etc.