The Baroness Elsa von Schraeder is a glamorous widow living in high-society Vienna. She's smart, beautiful, wealthy, and sophisticated—but she still doesn't get the guy.
Even worse, she loses him to a country bumpkin ex-nun.
The baroness and Georg are dating when Maria arrives on the scene. She seems cordial and refined, if a little manipulative. She's pretty sure she has marriage to the captain all sewn up, but she's not really on board with the whole parenting business. The children don't like her, and she's definitely out of her element when she tries to spend time with them. She's probably worried they're going to mess up her hair.
MAX: I get a fiendish delight thinking of you as the mother of seven. How do you plan to do it?
BARONESS SCHRAEDER: Darling, haven't you ever heard of a delightful little thing called boarding school?
MAX: Baroness Machiavelli.
There's trouble in paradise, though. When the baroness tunes into the fact that Georg like likes Maria, she makes sure to bring that fact to Maria's attention. She knows that will freak the naïve young woman out.
BARONESS: Now where is that lovely little thing you were wearing the other evening? When the captain couldn't keep his eyes off you.
MARIA: Couldn't keep his eyes off me?
BARONESS: Come, my dear, we are women. Let's not pretend we don't know when a man notices us. Here we are.
MARIA: The captain notices everybody.
BARONESS: There's no need to feel so defensive, Maria. You are quite attractive, you know. The captain would hardly be a man if he didn't notice you.
When this little exchange has the intended effect, the baroness seems pleased and immediately offers to help her pack. Maria bolts. The captain proposes marriage, and the baroness assumes she dodged a bullet. But she has underestimated the persuasive power of Notorious T.R.M., who sends Maria back to the family to figure out her feelings for the captain.
Once the baroness realizes that Georg's affections for Maria aren't going away, you can see her heart sink. Still, she removes herself graciously, in a way that spares the captain's feelings:
CAPTAIN VON TRAPP: Elsa.
BARONESS SCHRAEDER: Yes, Georg.
CAPTAIN VON TRAPP: It's no use. . .you and I. I'm being dishonest to both of us and utterly unfair to you. When two people talk of marriage—
BARONESS SCHRAEDER: No, don't. Don't say another word, please. You see, there are other things I've been thinking of. Fond as I am of you, I really don't think you're the right man for me. You're much too independent. And I need someone who needs me desperately. . .or at least needs my money desperately. I've enjoyed every moment we've had together and I do thank you for that. Now, if you'll forgive me, I'll go inside, pack my little bags, and return to Vienna where I belong. And somewhere out there is a young lady who, I think will never be a nun.
We forgive her for being such a schemer. She's vulnerable and humiliated, and this makes her more sympathetic.
At this point, the captain knows his heart isn't in the relationship, but he doesn't know why. The baroness sees it more clearly than he does. And it makes sense that she knows exactly when to scram. After all, she's a gifted hostess, so it's her job to know when the party's over.