But it turns out that Gaga had actually called the screen legend ahead of time to touch base about the performance.
"She had done me the honor of phoning me about 10 days before, asking if I minded the fact that she was doing 'The Sound of Music' medley and she hoped she didn't offend," Andrews told ABC News. "She was singing all the songs in my original keys ... and I said on the phone, 'That's very high.' She said, 'Well, yes, I wanted to do them as a tribute to you.'"
Andrews, who said she'd "been a fan for a long time" of Gaga, was knocked out by her performance of "The Sound of Music," "Edelweiss,” “My Favorite Things” and “Climb Every Mountain.
"The minute I got home from the Oscars I called her. ... I confirmed that I thought she was fantastic and had done a wonderful job, and I couldn't thank her enough," she said. "She really did a wonderful thing with the medley. She sang superbly and then so lovingly handed me the evening on a platter, if you know what I'm saying."
"As I say, I've been a fan for a long time but she's now a very new good friend," she added.
Andrews is also confident that Gaga could have a career in musicals if she wants it.
"I've been saying it ever since," she said. "I have, truthfully!"