If the dry cough is related to the medication, the doctor may change or reduce dosage.
An IVS size is an estimate, and may be in the normal range when considering the margin of error.
When a heart wall enlarges it may become stiff, and the lack of elasticity may reduce the filling capacity of the left ventricle, and/or lose contractility force. Either of which condition the cardiac output can be reduced causing symptoms of chest pain, shortness of breath, etc. I don't believe your mother's IVS, is a size that would be problematic.
Thanks for the question, and if you have any follow-up questions, you are welcome to respond.