Your old woman might be easier to convince if the boat
was a little bigger. 26 feet isn't really much space for someone used to elbow
That being said, there are books
to address your question: "Self-steering for Sailing Craft" by John Letcher, discusses everything from sheet-to-tiller to building your own windvane
Bill Belcher has a book on how to build a ghetto windvane
. not a good as Letcher's, but there it is.
For boats your size, there used to be a Plastimo
brand servo-pendulum windvane that was pretty affordable due to it's size.