Mother in Ragtime or Millie in TMM
Honorable Mentions:
Lilli Vanessi is Kiss Me Kate
Julie Jordan in Carousel
Amalia in She Loves Me
Bakers Wife in Into The Woods
Nellie Forebush in South Pacific
there's more but I would say these are closest to the top of the behind the first two.
"Did you know that if you take the first two vowels in Olive and rearrange them it spells I-Love?"-Spelling Bee
"It's night like this that hotel bars were specifically made." Light In The Piazza