I don't know who that is. Could you give us a pic or a link to one? Some actresses are very easy to change with makeup. They need to look for one with a changeable face.
Yeah, but sometimes she's an old lady with grey frizzy hair, sometimes she's a young woman in her twenties with bright pink hair. They could change her, but it would probably be easier to hire two people.
I suspect they would need the same bone structure though.. I don't know if Metamorphmagi can change that. And like fuscia said, movie makeup can work wonders.