bachelor-girl:

Note: An unmarried woman is called a ‘spinster’, ‘bachelor-girl’ & ‘bachelorette’. The word ‘spinster’ was very much used in the past but gradually it has lost its popularity because it has been used to refer to an old woman who has not been married at all, i.e. a woman who has stayed unmarried all her life. So, the word ‘bachelor-girl’ has caught up popularity and is the most common word used to refer to an unmarried woman who may marry when a suitable “bachelor” wishes to propose to her. And the term ‘bachelorette’, though not very popular, is used as an informal term, causally or for fun, to refer to an unmarried woman, mostly in American TV programmes. In addition, the expression ‘single woman’ is also being used and is fast becoming popular, particularly with the younger generation.