Bomb scare at Gatwick

http://www.independent.ie/irish-news/ryanair-flight-is-evacuated-in-bomb-scare-29111808.html

RYANAIR plane travelling from the UK to Ireland had to be evacuated after a passenger approached cabin crew minutes before take-off to tell them that there was a bomb onboard.

The plane was preparing for its scheduled departure from Gatwick Airport at 6.10pm (5 March 2013) when a woman, seated at the rear of the plane, calmly walked towards the front of the cabin and told crew there was a bomb secretly hidden in the plane.
Emergency personnel mobilised swiftly as police and bomb disposal experts rushed to the scene.
A woman in her 50s – who was described as being in a "disorientated state" – was immediately arrested by airport police.
The scare occurred minutes before take-off and forced Ryanair to evacuate some 100 passengers and 10 crew preparing to take-off for Dublin.
No bomb was found and the plane took-off over an hour later and landed safely in Dublin.

A Ryanair spokesperson confirmed that a "security incident" had taken place and apologised to passengers for the delay.

Wonder what the object was and what made her think it was a bomb?