Jordin Sparks is completely taken aback by the rape allegations against Nelly, and so's the guy next to her at baggage claim ... maybe even more so.
We got the singer at LAX and broke the news to her -- Nelly was arrested for allegedly raping a woman in Washington -- and her jaw almost hits the floor. Jordin looks downright dismayed as the news sinks in ... and it leaves her at a loss for words.
Sparks does manage to tell us she knows the rapper, and clearly ... the story's baffling to her.