Yes, I saw her in 'night, Mother on Broadway and the original Frankie and Johnny at Manhattan Theatre Club. She was amazing in both, and was generally regarded as one of the best stage actresses in New York at the time. I believe she has not done any theater since Frankie and Johnny though. She was announced for the world premiere of a Terrence McNally play called Unusual Acts of Devotion in 2007, in Philadelphia, but she dropped out. See the linked article.
She went into ROAD TO MECCA right after FRANKIE AND JOHNNY in NY and then did FRANKIE again at the Taper. I got to see her in both, along with the revival of CURSE OF THE STARVING CLASS. She was aces in all of them. So lived-in and at ease.
I saw her in all three as well, chrisampm. She was one of the great stage actors of that era. As good as she is on film, she was even more impressive on stage.
The night I saw her in The Road to Mecca, she and Athol got a bit flummoxed during their first scene, and she asked him if they could start over. He said yes, she went out the door, rang the bell (or knocked, that I don’t remember) and start over they did. It was so seamless I thought it was part of the play.