Drop her!
My husband has a brother who is 5 years older than him. They shared a bedroom as children and, according to my sister-in-law, they were always fighting and arguing! My husband is quite a self-contained person, so he seldom speaks about his younger years, before he met me, when we were both just 18.
My husband's brother married "The Woman from Hell". No-one in his family liked her - she really was that bad - but my husband absolutely loathed her, as she was the embodiment of everything he hated in a person! So, when his brother moved out of his parents house, he kept contact with him to an absolute minimum! Being an only child myself, who would have loved to have a brother or sister, I found his attitude hard to understand. At one point, they went for over 15 years without a single word passing between them!
In February 2018, his brother's wife passed away, aged 64. I thought then that there might be some sort of reconciliation between the brothers, but it was not to be! My husband said he wasn't going to the funeral of someone he hated, and he stuck to his guns! I asked him if he ever planned on ever speaking to his brother and he said it was highly unlikely! He has always been close to his sister who is 12 years older than him, and kept in regular contact with her. I like her very much - she's the sister I never had! She's now nearly 76 and in poor health. I know that when she passes away, my husband will certainly attend her funeral, but I also know that he will completely ignore his brother, who will also be there!
I don't like the situation between my husband and his brother, but I have eventually realised that I cannot change it! I also have a grown up son and daughter who are estranged from one another, and it breaks my heart, but I cannot change that either! My daughter, the older, has always been difficult, is jealous and resentful of her younger brother, who despite being disabled, is academically very bright, did well at school and has been a professional musician since his teens (he's now doing his Music degree) and made quite a lot of money from what his sister considered just a hobby. In the past, she has said some terrible things to him, so he has chosen to distance himself from her! She lives over 50 miles away, so it's not too hard for him!
In spite of being upset by my family situation, I do my best to have my own interests and friends and keeping busy takes my mind off something I can do nothing about! If your sister makes you unhappy and you really don't like her, then let her go, and don't feel guilty! Life is far too short to not live your own life to the best of your ability! Good luck!