Hi, thanks for the question. Coughing at night and feeling better during the day constitutes an clinical complex classically seen in heart disease. The commonest cause of this is heart failure. Knowing whether she experiences other associated symptoms like fatigue, breathing difficulties, swellings, fever and whether the cough is productive or not, and if yes, the color could be very helpful. A chest X ray and a cardiac ultrasound in the situation and key exams that shall put things into real perspective. Meeting a cardiologist to compound this with a proper physical examination could really be of utmost help. However while waiting, sh continues on her usually medication, low salt diet, prescribed diet and its advisable she gets shots for Hemophilus Influenzae and Pneumo 23 regularly. Thanks and hope this helps, Best regards, Luchuo, MD.