How would pretty be classified in this sentence [duplicate]
In the sentence,
You look pretty tonight
Pretty serves as an adjective and "look" serves more of the function of linking verb than action verb.
In the second sentence,
You look pretty gorgeous tonight.
Pretty does indeed serve as an adverb modifying the adjective gorgeous.
You have made some interesting observations here. The verb "look" is a linking verb here like "to be" instead of describing an action.