Has a beta blocker been offered? They can keep the heart rate down. I managed my afib for 7 years with Atenolol. There is a also new drug for heart failure, which it sounds like your Mom may have, hence the need for the diuretic. I am not sure of the name, but it is doing wonders for this disease, which my mother suffered from, making huge decreases in mortality. It is being fast-tracked and approval by the FDA and will be available in 2015. Wishing you both good luck in finding help. I would consider a 2nd opinion.
I know a few that are in afib every day all day long, dr says they are ok, they have to learn to live like that, I would go nuts, I have flutters and papa tigons they drive me crazy can't imagine being in afib rest my life,, they to take meds to try and slow the heart down, that's all they can do for them