The 25-year-old actress - who plays Alice Cullen in the film - believes that fellow actors including Robert Pattinson and Kristen Stewart will find it difficult not get overcome with emotion.
She told E! "I think we're all going to have wear waterproof mascara. It's been such an exciting thing and I think none of us are quite dwelling on the end yet because we still have the press tours and all that stuff. So it's still kind of exciting."
"It's probably going to be a tearjerker when we all realize that it's over."
Meanwhile she told People magazine that she has no regrets about decisions in her career and life.
She said: "I don't [have regrets]. Things have happened that have been unfortunate at times, but I feel like it's really how you take that experience and learn from it and grow from it. Everyone has ups and downs. I try not to regret."
She continued: "I feel like when I was first kind of thrown into this industry and this whole world, it was a little overwhelming, and everything seemed like the end of the world sometimes. You're focused on every little thing, good and bad."
Ashley added: "You kind of just have to ignore a lot of things and focus on your job and what makes you happy."