This about.com site has a nice list of famous African American women. You could help your daughter pick a few of these women, and then do some research either in physical encyclopedias, online encyclopedias, or even online. Just make sure whatever information you gather online has a legitimate reference behind it.
I wish I had seen this earlier, however depending on when the poster is due, I recommend American Legacy Magazine, the magazine of African-American history and culture. In most of its black history month issues, with the exception of 2009 are stories and pictures of African-American women pioneers. I can send back issues of the publication, if time allows. Let me know.
Hello, you can get a lot of data on Black history in the United States; anything you want like black slavery, Lincoln's bill etc, you just need to go to the right source. I use this site whenever I need to write any historical document. i hope it helps. it has a lot of legit info in it. Best of luck!