Didn't buy my sister a birthday gift

My sister's birthday was yesterday and when she woke up I told her Happy Birthday! Then I jetted off on my date and was gone all day. My sister did not want to do anything for her birthday. Her idea of birthday was sitting at home, alone, in her bedroom watching the last day of play at Yankee Stadium. My parents wanted to take her out to lunch or dinner, but she was too busy with the game. It was a 8-9 hour game celebration I guess. I would have been here at home not doing much of anything, and not spending time with her.

So I didn't buy my sister a birthday gift either. My justifications: she never wears anything I buy for her (the past 3 birthdays I have bought her very expensive outfits that are tasteful and she won't wear them), she never uses anything I buy her and complains that she doesn't like something about it, she complains about every imperfection, and my biggest reason of all is how she treats me (teasing me and calling me gay a few weeks back threatening, and did tell my dad). I do not like her. I thought a lot about this last week when I knew her birthday was approaching and decided to just forego buying her a gift. I could have even given her money, but she never spends her money or gift cards she is given. I came to the conclusion I buy gifts for friends and family who are deserving of gifts. I buy gifts all the time for people- I'm not asking for anything, I do it out of the goodness of my heart, and have no problem buying gifts for friends or family who treat me well. Sister doesn't.

Sister apparently was in a huff about it last night that I didn't buy her anything and my mom mentioned something about maybe it is the way she treats me, or I just haven't had time to give her the gift because I was so busy with a "great opportunity to go out on a boat with friends and cruise the ocean." I know it would keep things rosy on the home front if I did buy her a gift, and the thought of buying a gift is what counts, but my heart is not letting me.