I know Ron has explained this in his earlier thread, but I just wanted to confirm that I understand "not the least of which is her African heritage" correctly. Does that mean PW's blending of X, Y, and Z has already suggested her influences, not to mention her African heritage, which is also one of her significant influences?
It seems that you're asking about the overall meaning of the sentence. I would distinguish between the images that she uses and her influences. The sentence says that she uses a broad range of images (in her poems), and that her use of these images shows that she had a broad range of influences. Among these influences is here African heritage.
Take a look in All the Verbal Companion (or the SC strategy guide if you have older editions) for the chapter on Extra: Meaning, Structure, and Modifiers on 'Subgroup modifiers' for more on this.