In Faulkner's short story A Rose for Emily has a underlying theme of loneliness. A character like Miss Emily is with out a doubt depressed and lonely. Emily has a strong potential disposition for mental instability. The story was intentionally written in a dreary tone making way for the horrifying conclusion. For the most part the story gives us insight into the dark side of human personality. .
Miss Emily is a character that leads a repressed life caused by her upbringing and developing into a depressive state. For some time in the story Emily is portrayed as a very depressed person who never leaves the house and never sees anybody. A person like that is really seen to have a mental disorder or was the main objective to cover-up a murder? Most likely in Emily's case it is both going on at the same time. I think it is assumed that Emily had emotional scars but the story doesn't focus on that alone. It is really up to the reader that judges the scale of Emily's emotional distress. I think it is true that Emily's emotional state was on a downward spiral after she poisoned Homer. .
Emily didn't murder because she was mental. The murder came more from emotional hardship than anything else. After she murdered homer she became increasing insane. The fact is that she had to deal with the consequences of killing another person such as the disposal of the body, suspicion by others, and mental capacity to deal with the after affects. Emily couldn't deal with another emotional scar. She might have taken her own life if she was emotional stable. Instead she is fixated on how things could have been which turns into the story of her life. Emily's loneliness is manifested in her depressive state and emotional detachment from the world.