Explanation: You had it right. It is to inform because the author is simply telling her story. Despite how sad it is she is not trying to receive anything from the reader. If she was trying to entertain she wouldn't have been righting about her life story with her tone, especially considering it is a sad story about slavery, and if she wanted to get a reaction she would have taken a defensive or aggressive tone to the topic.
The author is not trying to argue a certain point, I can tell from the tone that they are simply trying to inform the reader what their live was like in their perspective.
