are you seeing a cardiologist?  That's really the big step.

What have they put her on? Is the cough from the heart pressing the trachea?
My cat has mitral regurgitation and the heart is enlarged. She had a bad
cough whcih is why I took her in. SHe is on enalipril and lasix, but alos we
have weaned her down to a low dose of prednisone. THe cough has kept away.
Some people really disagree with pred in a heart kitty. Indeed, it is not
ideal. I tried weaning her off once but then she coughed. So I kept her on
the very low dose every other day. We are trying to wean her off again, but
if the cough comes back, I will put her back on the low dose. I would rather
her be comfortable and happy for a shorter period than to have her being
sick.

Speak to your vet about diltiazem and an ACE (angiotensin converting enzyme)
inhibitor such as Enalapril and Furosemide (Lasix) a diuretic.

Diltiazem is a calcium channel blocker which, among other benefits, improves
relaxation of the heart and reduces contractibility- which in turn might
help reduce left ventricular diastolic pressure- which in turn should help
reduce pulmonary edema production- which is what's probably causing the
nasty cough.  Diltiazem might also reduce your cat's heart rate and left
ventricular hypertrophy (which will increase the inside area of the chamber
so it can pump more blood).

Enalapril prevents the conversion of angiotensin I to angiotensin II- which
is potent stimulator of myocardial hypertrophy (as in hypertrophic
cardiomyopathy).  Ergo, enalapril might also help reduce hypertrophy and
allow your cat's heart to pump more blood.  Enalapril also reduces
aldosterone secretion- which increases sodium and water excretion- which
reduces the edema that's making your cat cough.

Furosemide (Lasix) is a diuretic that would probably temporarily resolve the
pulmonary edema that's making your cat cough until the Diltiazem has a
chance to start working.  If you use Furosemide with Enalapril you'll have
to monitor your cat's blood pressure very closely because the combination of
these two drugs can cause hypotension. Also, cats are sensitive to
furosemide and prone to dehydration and hypokalemia, so, potassium
supplements should be given.  However,  potassium supplements can cause
hyperkalemia if taken with Enalapril.  Your vet would probably want to put
your cat on Furosemide until the pulmonary edema resolves, then taper the
dosage to the lowest that controls edema before starting Enalapril.

Best of luck,

Phil