I slip up sometimes on what’s been said in-canon and what’s been mentioned in commentary or ancillary updates, so if you are unsure why Selkie is coughing, it’s not a “drying out” affecting her. Her gills secrete an oxygen-transfering mucus when out of water to allow breathing, which builds up over time when out of water (which is pretty much all the time for Selkie). The mucus needs to be flushed with fresh water when it builds up too much, and things like cold dry air and rapid breathing from activity accelerate the mucus build up.
In other words, racing to the car in a blizzard was not a great idea.
"Nezzui Joh'de" translates politely to "Unlucky Poop". Selkie's using it as an exclamation but it's actually a moderate insult.
"Kransa bi Cholek" and "Baalu" are much worse and she really shouldn't be saying them at all.