girl friend vs wife

girl friend

noun
  • A female friend, especially a woman's. 

wife

noun
  • Synonym of woman. 

  • A married woman, especially in relation to her spouse. 

  • The female of a pair of mated animals. 

verb
  • to marry (a woman) 

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