Jonas, an avid cook, purchased the knife set during a trip to the Middle East, and stowed it in his carry-on luggage, US Weekly reported.
"We were going from the Middle East to New York, so (there was) tons of security, tons of screenings," Greene, 23, said on Lopez Tonight Tuesday. "We got through one, surprisingly enough."
But by the time the couple reached the second checkpoint, airport security "looked at us with these stern faces like, 'What's in your bag?'" Greene said.
Greene said when she asked Jonas if he packed the knife set in his carry-on luggage, he replied, "Whoopsies!."
"Whoopsies doesn't cut it," said Greene, who appeared in the movie "Twilight." "We were going to be arrested."
After explaining the mix-up, security allowed Jonas to stow his knife set under the plane.
"It was embarrassing," Greene added.