Name of movie based on Marilyn Monroe and JFK?

I remember it was mainly about a boy who was a neighbor of this this blonde gorgeous woman he had no idea was Marilyn. He would spy on her through his window. I remember she was working on an art piece and the boy was very curious about but she would say it was not finished. She had sex with JFK? while the boy was hiding. She was found dead in the end and the boy received a package from her and inside it was the art piece he was always so curious about. That’s all I remember. Anyone know?