The 27-year-old actress and Depp became involved after staring together in 2011 film 'The Rum Diary'.
"It is really hard when you spend your life living out of a suitcase," Heard told Company magazine in an interview.
"But it really does weed out superficial people-if someone is still with you after the second movie, then they're probably a good one! I like to trust people in general-it's the Southern girl in me."
The actress also finds it hard to tackle paparazzi that has become a constant part of her life since she started dating Depp.