WannaBe, you're right about Tomei, she is a knock-out. I just kinda love her subtle acting (her very unglamorous, quiet--Oscar nominated-- performance in IN THE BEDROOM is beautiful), but I know what you mean. I do stand by my Mary-Louise Parker suggestion.
Bates has indeed played the role time and time again, but oh she is so good at it! And I do believe she could be quite wonderful during Mattie Mae's final scene with Barb.
The other actress that comes to mind for the role would be Jean Smart.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"