Ashley Greene shows off some tummy on the cover of Cosmopolitan‘s August 2012 issue, on newsstands July 10. Here is what the 25-year-old actress had to share with the mag: On getting married: “I’m not one of those girls who sits at home thinking, By 25, I have to be married. Right now, I’m like I’m 25, I need to book my next movie! My parents have such a beautiful marriage. I’m not som…