Power - Emily had always served her father. She may have felt it was time for her to get what she wanted from a man.
Insanity- Emily lost her perspective of reality and romance in the world around her. If Homer did not want to marry her, she would keep him for herself anyway she could.
Anger- Emily may have thought: "He took me riding in my buggy. He promised me that he would stay with me in Jefferson. Now, he wants to leave. No, I will have not it!" She didn’t like the feeling of being lied to and betrayed after finally feeling hopeful about something.
And most of all loneliness — she is in denial and most of that feeling has to do with her loneliness. She poisons him and keeps him locked away in her room; she did not want to lose the only other person she had ever loved, so she made his stay permanent.
