The whole question is completely wrong - there is no adverbial phrase in this sentence, since a phrase cannot contain a finite verb in itself. What you are looking for is an adverbial clause, and thus the correct answer is after she finishes her homework, because it acts as an adverb - it answers a question when something is going to happen.
The studious Andrea is a noun phrase, will go is a verb phrase, and her homework is also a noun phrase.