she vs sis

she

pron
  • The female (typically) person or animal previously mentioned or implied. 

  • A person whose gender is unknown or irrelevant (used in a work, along with or in place of he, as an indefinite pronoun). 

  • A ship or boat. 

noun
  • A female. 

det
  • Synonym of her 

sis

pron
  • she 

How often have the words she and sis occurred in a corpus of books? (source: Google Ngram Viewer )