Wondering if maybe your dog might have had a cut before she walked on the salt? Sounds a bit odd because mine go out everyday for long walks and our roads are salted, they've never had any ill effects. I do rinse off their paws when they come back so they don't lick the salt. I don't know too many dogs that won't try tearing boots off and even don't want to walk with them on, it's too funny to watch. They sell something here called musher's paw...some people use that to put on their dogs paws if they find they have sensitive feet.