> My sister (subject) doesn't get up early. She (pronoun) often gets up at 9:00am.
Sentence 1: the main verb is ''doesn't get up'', which is third person singular. The subject is ''sister'' which is a noun and third person singular. The subject and verb agree.
Sentence 2: the main verb is ''gets up'', third person singular. The subject is ''She'', a pronoun and also third person singular. Its antecedent is the noun ''sister'' in sentence 1, which also third person singular. The pronoun and its antecedent agree.