bachelorette
An unmarried woman, especially a young one.
A bachelorette is an unmarried woman, especially a young one. The word is simply the female version of bachelor, which means an unmarried man.
You'll most often hear this word in the phrase bachelorette party, a celebration thrown for a woman who's about to get married. Her friends organize games, activities, and surprises to celebrate her last days as a single person before her wedding. Just like grooms have bachelor parties, brides have bachelorette parties.
Today, people mostly use bachelorette in the context of weddings and pre-wedding celebrations.