Is the portrayal of white women different from that of African women in Heart of Darkness?
There are three women in the story that we can compare in answer to your question. First, Marlow's aunt who helps him get the job in the Congo. Second, we have Kurtz's mistress in the "heart of darkness" or the central station. Finally, we have Kurtz's "intended" at the end of the story.
Marlow's aunt is described as "out of touch with truth" because she believes that the company is in the Congo to "wean those ignorant millions of their horrid ways." Marlow knows that the company is run for profit.
Moving to the end of the story, Kurtz's "intended" is also somewhat ignorant of the truth. Marlow hides from her what actually happened to Kurtz describing his death as follows: "His end... was in every way worthy of his life." Here , he misleads the woman by letting her believe that he died nobly for his cause and company. While he doesn't "lie," he does sheild her from the truth of the matter. Coupled with Marlow's aunt, Conrad has created two naive women.
Contrast them with the native woman, and you have a very interesting point of discussion. She is described in every way as beautiful and powerful. She seems to know what is going on and Conrad gives the impression that she is calling the shots along with Kurtz at the Central station.
In all, these women are portrayed very differently from one another regarding their race.