Used casually among friends and in informal settings to talk about single women. My bachelorette friends are planning a weekend getaway.
Pro Tip 2/3
Age Neutral
Refers to any unmarried woman, regardless of age, and doesn't imply youth. Even as a bachelorette in her 50s, she enjoys her independent life.
Pro Tip 3/3
Not Gender Neutral
Specific to women, never used to describe unmarried men; they're called bachelors. My aunt is a proud bachelorette, while my uncle is a lifelong bachelor.