I feel like no one cares

Hello,

Has anyone ever felt like no one cares and there is like built up anger in you? I have an older sister that has been the trigger for my anger. She is manipulative and has told me things like I was jealous of her and that I was jealous of her life. She has told me hurtful words that led me question about myself as a person. As of right now, she chose me to be her maid of honor for her upcoming wedding. I feel conflicted due to not wanting to be her maid of honor due to the things she has done to me in the past. I feel like she is wants to get her way somehow. She and her new fiancé have been really rude to my boyfriend and my boyfriend has not done anything to them. My sister and his fiancé claim that my boyfriend is competing in some way. I really don’t feel like being a part of this wedding. Sadly, my parents do not approve of my feelings and are making me participate. My sister has really left me out due to wanting to hangout more with her fiancés sisters rather than me. And also she has blocked me on social media and she still wants me to be her maid of honor? I feel sooo confused. Can someone help me with this situation