Highly concentrated salt water tends to damage most living things if it's internalized, but as for Shayan, the roots of the plant she's bonded to are in her body, so if she was immersed in salt water she'd have to actively drink it for it to be absorbed into the plant.

Even then, the entire point of this plant is that it can regenerate from nearly anything. Dehydration would probably temporarily wither it, but it wouldn't die.

As for her creations, while they are altered by crossbreeding they are just plants for the most part. The ones that don't exactly absorb water for sustenance (like the carnivorous ones which get both liquids and nutrients from their victims) would probably be less susceptible simply because they're less likely to absorb the salt water that's presented to them, but the rest would absolutely be affected.

Anyway, that's my opinion on Shayan in particular. If she was hybridized with a different plant or had roots emerging from her skin to either collect moisture from the air or the earth, I could see it making sense for salt being a major sticking point, but with everything but the vines internalized there's much less to worry about so long as you don't guzzle it.