It sounds like you have been conditioned to worry too much about how your sister behaves. I have noticed that in some cultures this sort of thing happens where god forbid a sister behave badly and it will ruin it for all the family. Personally? I think this is unhealthy and that your sister should be able to live her life the way she wants and the same for you too. Yes, enjoy the chocolates, watch a video and learn how to dance, learn how to enjoy your OWN life and let go of always having to think how others behave will ruin your life somehow so you don't really end up like the name you picked "never happy".