I would always write first about the person, inevitably a woman of a "certain age". My last offering for a short story was about an artist who I had to portray as unworldly, possibly unkempt, and yet had to be attractive to the hero. For that to work I had to make her love interest completely the opposite, ie, he fell for her because she was "different". I have written characters with a plot in mind but once I start they seem to go off and do what they want to and I struggle to keep up with my own story.