grammar - How do you modify an adverb with another adverb?

Not all adverbs are allowed to modify other adverbs. The adverb severely cannot modify another adverb.

You could correct the sentence by saying "extremely severely" or by saying "it had a severely adverse impact on her".

How do you determine which adverbs can modify other adverbs (or adjectives or verbs, for that matter)? I don't know; I haven't found any lists online, and none of the dictionaries I've checked classify adverbs according to what they are able to modify.