I thought as Claudia, that must be "The Moon in the River", one of my absolute favourites, based on "Philadelphia Story" (You know: Katharine Hepburn playing the uptight socialite)
It so well written, true to the storyline on Philadelphia Story, but with the approach of it own. Wonderful fic!
But if it not, then I am lost
***
My lovelife involves me and me alone.