I concluded I am a terrible person because no matter what I do, my sister is not happy.
I was wrong to think that meeting her out the evening of her birthday was enough. I was wrong to buy my step-mother a Christmas gift. I was wrong not to cancel my plans a few weekends and instead be with my sisters. There are other events in my life that make me wonder if I really am a bad person. I recently switched jobs because my old boss was very demeaning; other people have left there for the same reason. My fiancé has told me on a few occasions that I was rude. (Even though no one else in the conversation considered me rude.)
Up until recently I never had self-esteem issues. I cancelled plans with friends for this coming weekend because I think I should not socialize at all. A person can only be beat-down so much.