Continuity mistake: When Megan is outside the supermarket asking people to sign her petition, a woman walks up and begins writing on the clipboard. In the first shot, the cap is on the back side of the pen. From the next angle, the woman is scribbling and lifts the pen to show the cap covering the tip that she was "writing" with.
Factual error: When Leavey begins her training at Parris Island in 2001, she and all the other Marines are wearing MARPAT (Marine Pattern). In reality, MARPAT would have just been designed, and not manufactured until early 2002. The standard camouflage for Marines at the time was M81 Woodland.