I have to say I totally agree with BlackHoney. When I first heard this I had to pause for a sec. Nina Simone is a woman of great depth and mistery, intrigue, passion. When you listen to her sing, you could feel that woman's soul coming through her vocals. As much as I love Mary, and I do, I've bought every single album she's put out even if I didn't like most of the songs. But this is different.
This role calls for an actress who knows a thing or two about acting. I realizee that Mary resembles her a little but still. I think somebody like Angela Bassett could really pull this off. And its not the ghetto thing because I feel if your a seasoned enough actor you could definitely get past that.
I love Mary (musically) but I really don't see this being a good casting choice.