That's a question I've never thought about before! I guess my answer would depend on a number of things: Whether the film is going to be a comedy, a tragedy, or just a biography, and whether I want it to be realistic, or not.
If I didn't care about realism, and wanted to flatter myself by going for out-and-out glamour, then I'd pick screen siren, Rita Hayworth.
(Source: http://ymperia.com/yaiya/?p=4750)
The reason I'd pick Rita (apart from her glamour) is because of the colour of her hair - and her eyes.
As I'm a brown-eyed red-head, this unusual combination rather limits my choice of actresses to play me as, while red hair is itself quite rare, occurring in only 1-2% of the population, those of us with brown eyes are even rarer - as most redheads have blue eyes, or sometimes green.
I'm not choosing a fake redhead, as I think you can always tell the difference. Real redheads always can, anyway, and I hate that these days I have to give mine a helping hand!
To play me as a child, I'd probably have to choose Bonnie Langford, even though I've always hated being compared to her! She's got the right eye/hair combination, though - so she makes the grade.
As a teenager, I'd pick Molly Ringwald, as I really like her combination of vulnerability and comic timing.
Finally, to play me in my twenties and early thirties, I'd choose Karen Gillan - who again meets the eye/hair colour combination, and is a superb actress. (Watch her in "Let's Take Manhattan", if you don't believe me.)
(Source: http://www.fanpop.com/clubs/karen-gillan/images/28109000/title/karen-gillan-fanart)
I have no idea who could play me when I was older than that, so I'll just have to split my biopic into two parts, and choose the actresses for the sequel another time. Or maybe I'll just wait for Karen Gillan to age!