I assumed that she was dating James Woods, as they were together during the filming of “Holocaust”.
Now those two couldn’t be more different politically, LOL!
I looked it up: Cazale died in March 1978, and
The Holocaust came out a month later, and she married Gummmer six months after Cazale died. She supposedly cared for Cazale until he died. But I guess she could have dated Woods when they were making the movie, no idea. But they may not have had the same politics back then, and people weren't all up in it, then.
Nicholson said they had an affair in the 80's. She is still married to Gummer, but she is "dating" Martin Short.