Lena Headey Fights The Power In 'Dredd'
In the script, Ma-Ma is described as being in her late fifties or early sixties with a scar running down her face. There's no official word yet that confirms the casting so take this with a grain of salt. I'd assume if they don't go the aged route, they'll simply scar up Headey as is and send her to set.
Then again, maybe they will age her. You know how those make-up people love to show off. Seems like a waste of liquid latex when the production just could have hired Betty White. She's so hot right now.