What is the feminine counterpart of spinster?

In English there are no masculine or feminine forms. English uses gender specific nouns for male or female.

Originally, the noun 'spinster' was a Word for a young unmarried women (since it was they who usually spun thread into yarn), and eventually applied to unmarried women who were past the usual age to marry. Today the Word 'spinster' is considered a negative term.

Since the roles of males and females were not equivalent, gender nouns for males or females may not be equivalent. For example, the closest noun for a male who has never married is 'bachelor', but a bachelor can be a man of any age.

Today the preferred nouns for people who have never married are bachelor for a man, bachelorette for a woman.

Language changes with the needs of society.