I believe the point of the response you got is that your proposed topic, Emily Dickinson, does not meet the requirements of the assignment because there is no focus on a particular element or pattern of development in her poetry and because your proposed topic sounds as though it includes a study of Dickinson, rather than a study of her work.  I am by no means an expert on Dickinson's poetry, but your research might include reading all of her poetry chronologically to see if there is some pattern of development or to see what elements in her poetry you might want to focus on, for example, her use of extended metaphors.  If you do want to focus on Dickinson, you will want to be careful to distinguish between what she actually wrote and how her poetry was sometimes "cleaned up" for publication.  My understanding is that there are differences.  Certainly, Dickinson's work is worthy of study, to either trace her development as a poet or to focus on some element of her work. 

I need help developing a topic for my final English paper on literary analysis or patterns of development among authors.

This is an excellent project. Here are some suggestions. 

First, since the object of the paper is to look at development in an author or literary movement, you would need to examine at least two works. So, the first thing you need to do is to read two works of one author or literary movement (perhaps an early one and a later one). 

Second, you would need to compare and contrast your findings. Ask yourself these questions: Was there change? Was there development? As you ask these questions, I am sure that you will gain more insights. 

Finally, create a thesis and write about your findings. Most good essay have one main point.