To my mind it could be either. You're quite right that in these constructions both words can directly refer to the noun (eg. a "cheerfully playful" child is cheerful and playful). In this case, however, my initial reaction is simply that the writer was trying to be far too clever and it's unlikely that the meaning is particularly worth bothering about. It's "showing off" writing and is not, I think, primarily about conveying meaning.

It doesn't make sense (to me). 'seductively' is an adverb, so it has to modify 'nauseating'. But what does 'seductively nauseating' even mean ?? How can something be nauseating in a seductive manner ? The words conflict. I honestly believe the writer was trying to give the sense of the tactility being nauseous, yet seductive at the same time. The writer's actual words don't say this and are just confusing to me.

a tactility that is nauseating in a seductive manner. Adverbs are modifiers that don’t directly affect nouns so it makes more sense that it would be modifying the adjective.