Mila Kunis is not single at this point. It's hard to even spot when she was single. She started dating Macaulay Culkin in 2002, when she would've been around 19 (she's now 29), and their split from "some time ago" was announced in January 2011.
Last year, she started dating Ashton Kutcher, who just filed for divorce from Demi Moore in December. It's possible Ashton and Mila will get engaged at some point, since they seem to be on a serious path. But Mila is on the new March 2013 cover of Allure, and she told the mag, “For four years I was single. An amazing time. An amazing time. I love being single.” Then maybe she should do it more often?
Anyway, she also talked about getting partly nude in Friends with Benefits: “I showed sideboob. I don’t need to show ass. You get one or the other. You don’t get both.” Ha! And she also shared more frustration with the paparazzi for stalking her and telling everyone where she is at all times. That does sound frightening.
Sources: Just Jared, CBS News