My sister (29f) and I (26f) don't get along. For most of my life she has belittled me and during our childhood she was the primary bully in my life. I had others in school, and I struggled socially. My parents weren't good either and they let it happen. But my sister always saw me as not deserving of anything good. She talk like me having a single friend was too hard to believe and that I didn't deserve it. She called me unlovable and said no guy would ever want me.

She was always the first to laugh when kids at school bullied me or when it was talked about around others. There were times she defended people excluding me saying nobody wanted "that thing" hanging out with them or on their team. There were never any good sisterly moments and the best days were ones where she was busy with something or someone else to notice me.

I have seen her twice in the last 8 years (excluding this current incident) and both times she was just as awful. The second time was while I was engaged to my husband and she disparaged me and attempted to convince my husband he was better off without me. She found a lot of joy in imagining his family, specifically his mother, hating me. And I admit that before that time and before I met my ILs, I was worried given my track record. But I have a wonderful relationship with my ILs and my husband's parents, MIL included, are like the parents I didn't get to have growing up. They're wonderful.

My sister is also married and I saw her at a party at our grandparents place over the weekend. I heard her talk about how much her MIL hates her and she was telling some cousins how she can't do anything right by her MILs standards, how MIL wants her and her husband to divorce, how she's the outsider and judged for every single things she does. How her MIL has insulted her. And I loved hearing it. At one point I even started laughing with my husband about it because of how much I enjoyed it and how good it felt for her to experience some of the things she wished on me.

My sister saw us laughing and she stormed over to ask what we found so funny and we were like oh nothing and moved away but she acted up and got thrown out by our grandparents who told her was wrong to start a fight over anything after how she treated me. They told her they gave her more chances than our parents because she wasn't taught better by our parents but that she was reacting like that to laughing when she has repeatedly laughed about much worse and said and done much worse to me. And that she would laugh into my face while I was laughing with my husband. My sister was not expecting our grandparents to take my side. I told my grandparents how much I appreciated them for doing that. And I do. Still do.

But an aunt said I was wrong and so were my grandparents. She said we all know how my sister is and if I want to be better I shouldn't laugh at misfortune happening to my sister. Then she told me I could have been a better sister to her and supported her instead of laughing. And I argued with my aunt over it but she remained firm and said I really got to my sister. The way she was so sure I was wrong made me doubt myself a little and I don't know if that's old issues resurfacing or not.

AITA?