I think your wife is right, it's Wood Avens, Geum rivale.
It's very given to strange flower forms - whether through hybridisation or just as sports, I'm not sure. I have a plant in my garden which has a double flower just like yours at the moment, although all the other flowers on the plant are single. And I have a photograph of one at Salt Lake Nature Reserve in the Yorkshire Dales which was cristate, with leaf segments among the petals - just the one plant growing amongst many other wood avens of normal type.

I think I remember wood avens from around Ardtalla, along with a lizard basking on a rock, and swimming with seals in the sheltered bay. But it was a long time ago!