I think she was also nominated for her role in this movie. I certainly don't think she matched Viola's performance in this film, (the character I don't think allowed it), but she was still very, very good... and having watched Hillbilly Elegy recently where I think she was extremely good I think Amy is joining the greats.
I noticed, while watching the movie last night, that there were some very long sequences.... rare in today's movies. And while reading about the movie on IMDB it confirmed that this impression was right... some very long sequences, like the one you mention with Davis and Streep. I love scenes like that because to me it really showcases great acting... almost like a live theater production.
It would be remiss of me not to mention Phillip Hoffman who I think did a masterful job at 'subtlety' in his role in this movie... reactions, his expressions.. and this with what I thought was a bit too contrived dialog. I understand they wanted to create 'doubt' with his character but some of his dialog was a bit strange... Meryl's reactions to him, however, was masterful.