Norvasc is a calcium channel blocker, which doesn't usually cause a cough. The other med she was taking may have been an ace inhibitor, and they definitely cause the cough.
Atenelol is, I believe, a beta blocker. I've not heard of anyone gaining weight from a beta blocker, but who knows? Perhaps her doctor could reduce the amount of the Atenelol and add back the Norvasc...the combination may do the trick.
How high was your mother's BP without meds? And what is it typically on meds?