I leave for work at 7:00am. My sister never goes straight to work. She goes to my parents house first.
Sentence 2 : The predicate is "goes", which is third person singular, Who goes? - "Sister" is a noun used as a subject and it is the third person singular. The subject and verb in this sentence is agree.
Sentence 3: The first predicate is "goes" which is also thrid person singular. Who goes? = "she" is a pronoun used as a subject and it is third persona singular feminin. The pronoun and its antecedent agree