It seems that Elsa smiles after Donovan drinks from the false grail implying that she knew it wasn't the right one.
Did she betray him?
Science Fiction & Fantasy Stack Exchange is a question and answer site for science fiction and fantasy enthusiasts. It only takes a minute to sign up.Sign up to join this community
If we look at the script and the film's official novelisation (itself based on the script), we can see that Elsa clearly set him up to fail.
DONOVAN: I'm not a historian. I have no idea what it looks like. Which one is it?
ELSA: Let me choose.
DONOVAN: Thank you, Doctor.
Elsa and Indy exchange looks. He thinks he is seeing her in her true colors.
Elsa chooses a cup -- a solid gold, emerald encrusted goblet.
Donovan instantly takes it from her.
DONOVAN: Oh, yes. It's more beautiful than I'd ever imagined. This certainly is the cup of the King of Kings.
Elsa removed her hat and carefully picked up a shiny cup encrusted with sparkling colored stones. Donovan instantly grabbed it from her and held it up to the light. “Oh, yes. It’s more beautiful than I had ever imagined. And it’s mine.”
Indy expected Elsa to protest, but she remained silent. The knight’s face was implacable, revealing nothing.
Since we already know that she's a competent grail scholar, her mistake was unforgiveable.
I thought there was a change in the movie to add a "?" after the part were Elsa says "it would not be made out of gold", but I'm not sure... But if you watch the movie on Netflix with CC on you can clearly see it's not a "?" after Elsa say "it would not be made out of gold." but a "." Elsa is making a statement, plus, when Donovan is about to drink from the false grail the screen quickly flashes to Elsa slowly smiling. I think she purposely chose the wrong Grail. Elsa also had motivations, 1 she wanted the grail for herself. 2, she liked Indiana a lot more then Donovan, and 3, she lost her allegiance to the Nazis when she saw them burning the books, you can clearly see her crying.
My first initial thought was that she had given him the wrong grail on purpose, but then at the same time if she had, why did she seem so surprised and horrified that he was killed by drinking from the grail she picked out? The knight stated very clearly that the wrong grail would "take it(life) from you." I'm sure it was on purpose but still, just a thought, perhaps she was just freaked out by HOW the wrong one kills you.
I think she did purposely give Donovan wrong one. He sealed his fate when he stated he wanted the Grail for himself. Elsa's allegiance wasn't to him but to the Nazi's (thus also Hitler). There is no way they would allow Donovan to keep the Grail. Historically the very reason Hitler had real life artifact or relic hunts was to make himself and his forces more powerful. So why would they allow Donovan to keep the Grail?