I respectfully disagree, RentBoy. Without the second act, none of the major themes of the musical would be fully expressed, the second act deconstructs the idea of happily ever after, it explains that all actions have consequences, and it completes the characters' journeys. It'd be too easy for both the writers and the audience to end the show with Act I, Act II is what makes the show so compelling, unique, and thought-provoking.
Also, it wouldn't make sense for the Witch to sing any part of "No One Is Alone," it'd be completely against her character, remember she's "not good, not nice, just right."
"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"