OH I have seen this before: 25 - year old spinster....LOL
(it is non-British English and not in use now in England)

I don't like Bachlorette either... as it is
a) feminisation of male
b) Americanisation

just say un-married
here it is difficult because single means one doesn't have a partner and if you have a partner but are not married = Haram

I also hate it when I fill things in and I can't tick Miss... I MUST be Ms. I am proud to be Miss not ashamed... neo-feminism?

But - spinster... LOL this image of some sour bitter old biddy knitting cardies comes to mind! Not quite there yet!