Here’s a great story from the Playbill article on her death:
In a particularly memorable chain of events, Follies director Hal Prince asked her to simultaneously stand by for Jane Russell as Joanne in Company during the run of Follies. One evening, after stepping in for Yvonne DeCarlo to perform as Carlotta, Ms. Smith found herself shuttled between the two theatres, finishing the song "I'm Still Here" and then quickly changing costumes to immediately step in for Ms. Russell to sing "The Ladies Who Lunch" in the second act of Company. She is, as far as is known, the only actress to appear on Broadway in two different Sondheim musicals in the same evening.