Thanks for writing your query to us.
Since your mother in law is diabetic so she is more prone to heart disease
. Breathlessness, cough
can be either due to cardiac causes like heart failure
or respiratory causes like infection. To know the exact cause of the cough & breathlessness she needs to be examined first by a physician. An Xray of chest & 2D Echo can precisely give us an idea about the reason for cough & breathlessness. Just treating her symptoms will not help her , she needs a detailed evaluation to treat the root cause for her symptoms.