Monique's character wasn't supposed to be a "representative portrayal" of Black women. Her character in the book was a crazy bitch, not a stereotypically angry Black woman. She was mental and took her issues out on her child. She wasn't meant to be seen as the norm. Both the director of the movie and the author of the book were Black and the white masses weren't intended to be the target audience. Not only that, but the author based Precious and her entire situation on the lives of real young girls she encountered while working as a literacy teacher in the Bronx. The actress who did end up playing Precious was chosen out of the hundreds of girls who auditioned for the role because she was the only one who hadn't been molested or beaten (and Lee Davis didn't want to exploit the other girls who had been). So I don't see what the problem is with raising serious issues in the community that need to be addressed.
Monique played the hell out of that role, so I'm glad she won best supporting actress. I'm still mad that Gabourey Sidibe didn't win Best Actress for her portrayal of Precious. She earned it.