With regard to your question, at least one source (as required by eNotes) must be an enotes source. It is your choice whether or note you wish to use it. There are a number of sources online that highlight Ms. Porter's life and writing, which also describe the kinds of things she wrote about (which would provide information about what influenced the author), as well as sources that outline this information.
Please note that I have not included any "questionable" sources in terms of the reliability of information based upon credible (or the lack thereof) research.
The first source that I believe would be helpful is found at the PBS site:
The second source, as noted, is from eNotes:
The next source specifically notes people who helped Porter find direction in her writing:
I hope that these sources are of assistance to you in finding the information that you require.