Fighting African Dragon/Demon; myth/fantasy, children's

a child or 2 siblings (can't remember) in africa have to defeat an evil dragon or demon (I think it was female, I can't remember if it was a dragon or demon). They succeed and slay the dragon/demon.

I read this book as a child 20-25 years ago at the public library in Elyria, OH. It was an illustrated childrens mythology/fantasy book; had lots of red, orange, and black in the illustrations, lending to an overall darker/grimmer feel to the story.

I remember that it was a good story that stuck with me for a long time, but now I can't find it.