What am I doing wrong?

I have a twin sister. It seems like she is always against me for whatever reason. Against me in ways where I could say something about how I feel and she tends to go the opposite way. I often talk about certain things in a "small talk" kind of way.

For example, I purchased a shirt online that I thought was cute. When I got it and I tried it on, I thought it didn't look right on me because of the cleavage cut. I have small wide set boobs. After trying on the shirt I said, "ugh my body isn't made for shirts like this lol" She could have said something simple like, "yeah you're right or it looks good on you". Something small. But instead, she criticized my mental, comparing me to other women who are confident and telling me that I shouldnt have gotten the shirt in the first place because it's not my personality. It's always something where I feel the need to defend myself. But when I do, she plays the victim telling me that she can't say anything without me getting upset and I need to do some shadow work to see what kind of person I am. She literally leaves me confused because I never asked for her opinion. It was simple small talk.

Today, I was playing a video game with random ppl online. While my nephew was playing, I was saying things like "you got this! Get him! Just one more hit" but when I was playing both her and my nephew was saying that I would lose and I suck. After I lost my nephew ran off laughing at me. I get it, it's how kids are. But I yelled out, "man it would be nice of you guys cheered me on. Sheesh, once in a while would be nice". My sister butted in to say "it's only a game, you're just mad you lost. Stop trying to make it about anyone else." I get it. It is just a game. But why is it that she only ever sees me as wrong. Why not my nephew? She said it would be fake of her to cheer me on. She even Googled something that said, a person who gets upset at a video game is a person with control issues who has a violent mentality. Me??? Violent mentality? Just because I said it would be nice of they supported me once in a while? She always blame shifts then when I defend myself, she goes into playing the victim as if she was the one hurt and I'm causing problems. It was a small comment that never needed to get out of control. She always has an opinion about any and everything I say or do and makes me out to be the crazy one. What am I doing wrong? I just don't get it? I know I should stop saying things to her or around her all together. But why does she always pick on me then I end up apologizing at the end? Please help!