Fantasy: Diana Wynne Jones, A Sudden Wild Magic, has a rather splendid elderly witch who is essential to the plot and Impossible to keep under control. It also has an invasion of another planet which can only be carried out by women. They get there in a converted coach. It all makes sense at the time...
Fantasy: Patricia Wrede, The Seven Towers has a sorceress called Amberglas who may possibly be the funniest Wise Woman in fiction. (The first chapter is slow until she turns up and the book takes off in several directions.)
If you don't mind books set very late in a series, Lois McMaster Bujold's Gentleman Jole and the Red Queen is what happens to the original heroine after the original hero Aral Vorkosigan has died. Most of the Vorkosigan series concerns itself with her not-a-mutant-dammit! son Miles, but she grows up through them from the thirty-ish that she is in the first book. I'd recommend the whole lot, really, just don't start with Ethan of Athos by accident: it's rather a side-issue. And they're not appropriate, obviously, if what you want is only women over forty as the protagonist.
Detective, sort of: Hazel Holt's Sheila Malory books are about a widow who stumbles on crimes with Miss Marpley regularity, and scandalises her lawyer son by investigating things. No graphic violence!