I was looking at an old marriage certificate (circa 1942) at work today, and noticed that the the bride (aged 18) was described as a "spinster"! I never realised that applied to any unmarried woman (unless she was thought old to be unmarried at 18).
All first time brides were known as 'spinsters' [and possibly may still be so - but I haven't got married for a while so I don't know] and their age had nowt to do with it. It's interesting how the word now [to those aged 30 and younger]conjures up an image of a a lady past her prime.
(Chalky) You don't need to be under 30 to think of a spinster as unmarried and no chicken. The word was a bit old-fashioned even in my childhood (40's - 50's), and mildly derogatory. Its original meaning was "female spinner" (of yarn). This was presumably thought a proper way for unmarried ladies of a certain age to occupy their time, in the absence of vibrators, though who knows.