Mr Essouira was a bit nervous too about the dangers of light aircraft before I started learning. After he went up for a trial lesson himself his anxiety faded. Find a competent, experienced instructor that will treat your girlfriend with respect and explain how it all works - they'll alleviate her worries in no time. She may feel more confident with a female instructor - or someone older. Be patient - and remember she's only worried because she doesn't want anything nasty to happen to you !
(by the way, I too have had an engine fail and landed safely in a field)