girlfriend vs the love of one's life

girlfriend

noun
  • A female partner in an unmarried romantic relationship. 

  • A fellow gay man, especially a friend as opposed to a sexual partner. 

  • A female friend. 

  • A term of address for a female friend or among gay men. 

the love of one's life

How often have the words girlfriend and the love of one's life occurred in a corpus of books? (source: Google Ngram Viewer )