The correct option is B until she got ready
An adverb clause is a group of words containing a subject and a verb,
and it functions as an adverb, by modifying an adjective, verb or an
adverb. Adverb clauses generally begin with a subordinate conjunction
(since, because, while, etc.)
From the options, "until she got ready" is
an adverb clause of time, 'until' is a subordinate conjunction that shows time, hence option B is correct.
Option A is incorrect because it is a phrase.
Option C is incorrect because it's a word, not a clause.
Option D is incorrect because the answer lies in B.