Sibling angry because I try to help parents adhere to low sodium diet; feels they should eat anything they want despite CHF. Advice?

Sandwich a stroke may or may not make Mom a vegetable as you know but she would not enjoy the build up of fluid in her body. Can't eat because of a belly full of fluid, can't breath because the waves are lapping in her lungs and legs so swollen the skin pops and she has weeping ulcers. Not a pretty sight.