"I'm always here and there – everyone in my industry is – and that's why a lot of relationships are fleeting," the actress, 25, tells Marie Claire in its November cover story, on newsstands Oct. 23.
And while the upcoming Nov. 16 release of Breaking Dawn – Part 2 has put a spotlight on the supernatural franchise's real-life romantic ups and downs between Robert Pattinson and Kristen Stewart, Greene's own challenge is balancing her career with her personal life.
"I've gotten very good at detaching whenever I have to go away for three months, which I realize is hard on friends and kind of selfish," says the Florida native. "You go on a couple of dates, and then someone ships off to do a movie. It's not like you're going to fly out and see them, because it's not serious enough for that."
But no one can accuse her of being a different Ashley, even while on the celebrity fast track playing Alice Cullen.
"After the movie [Twilight] came out, some people said, 'You changed,' " she says. "And I said, 'I haven't changed, dude. Your opinion of me has changed because I'm working on this film.' Trust me, my parents would let me know."
Courtesy Marie Claire