In Edge of Tomorrow

Yep, her accent is up and down, accuracy-wise. I'm from Birmingham, Alabama, and have lived in Alabama and Georgia my whole life. Some of her lines are believable-- although the extremely thick accent like she uses is starting to fade away in the heavier populated areas as older generations pass-- (there's more of it in areas that are in the middle of nowhere), but the majority of her lines are noticeably faked. It's usually pretty easy for me to tell if someone has a southern accent for real, or if it's not real, and I could tell hers was fake pretty quickly. Generally, when an actor/actress uses that heavy of a southern accent (unless the movie takes place in the past), it's a sign of an attempt to overcompensate and oversell. But more specifically here, like red_skin said, when she was reciting her lines about the Sergeant's dislike of gambling, she was all over the place. The most notable point was when she said something about "...fate being in hands other than our own." (or something to that effect). When she says "our own", it's 100% clear she's either from the UK or Australia. I also agree with people wondering why she changed it in the first place. It wasn't necessary for this movie.