Why does my sister do this???

I have one word of advice. Persevere. A good quote from a movie that has helped me before.

"Thomas Wayne: And why do we fall, Bruce? So we can learn to pick ourselves up. "

I think it's a sister thing.
My sisters sometimes say some really hurtful things, at which point I'm usually extremely peeved with them, to put it mildly.
Though, I don't think that they mean to insult in such a manner. It's like one of those moments where you wish you could take the insult back, but you can't coz it's already been said and sometimes you feel too pig headed to take it back (happens with me sometimes).
But yeah, usually when you don't retaliate, the argument calms down and should be forgotten within the next..oh, 10 minutes.
Hope all improves with your sis. Just try not to let it get to you insha'allah.

try to determine if you BOTH want to work it out or not, then try to solve it.
also, try to give each other more 'breathing space', you might be in each others face all the time, that gets on nerves. as in you have to 'conform', or think you have to conform if you're always together.

let her know she can do whatever she wants, tell her you having different ideas of what things to do or how to achieve them is just natural, and it shouldn't stop her from doing what she wants.

also, remember to always focus on what started the argument, don't go off on tangents, and NEVER, I mean never bring back something from the past unless it's absolutely relevant. don't say stuff to get to at her, stay as calm as you can be, silence is not good, nothing gets solved that way, and it's too pacifist, but neither is shouting or insulting-'m not implying you do, but everyone does have a limit.

I'd say pause for a second-or more - when/if an argument develops, then talk, and remember keep your attention on the reason for the argument, and on what the other is saying, try to understand it as it is being said, ask if you don't understand, communication is the key to solving all problems.

say things from your perspective, say 'I' when you describe emotions, that seems like a big duh, but that does make you both aware of each other, that the other might be hurting from what was done/said, also, emotions are ok, no need to be afraid/ashamed of them, and if you're at fault, apologizing is the right thing to do.

one more thing, remember that you Are sisters, and thus are part of a whole, not opposites, and that you don't need to to hit under the belt, rather accept the other person.

I hope that helps, and God willing you'll be well all your days , ok that was too dramatic, anyway, good luck,,

Assalamoalaikum

It happened to me too, when we were young. Although I am the oldest, and her being exactly a year younger to me I was even scared of her as she would beat me up. Then I got married , I was very young and the rift grew but somehow seeing me take care of a family changed her perspective a little. 7 years after I got married she got married too, and since then we have been so close, Allaho Akbar! It feels so nice, she didn't trust me in the beginning because she thought since she has openly called me her enemy before that i would taunt her all the time about her choices or way of life or whatever, but I dont and I dont even compare ourselves in my mind, and she's Alhamdolillah very happy anyway,so things are good.

My advice would be ignoring and patience.

Do not confront her, if things go bad, just get up and leave. be the one to keep cool and one day she'll come back.

When we were younger somestimes i would give my lunch money in school for charity or other school activity, then during lunch I wouldnt have money to eat or drink, mostly I would bring along a small snack from home but sometimes I would give my money on impulse, she was normally given more if not double than me, I would ask her to give me a sip of water at least n she'd refuse heheh thats apart from the extreme insults n things that went on for around 15 years hehehe

Alhamdolillah we are very close now, I love her and I never think back.
Be the bigger one, she'll come around one day too. InshaAllah
P.S dont forget to make dua

I have a similar problem but it doesn't seem to be a big problem.Many times it can be cause from misunderstandings that can be easily dealt with together other times it takes an adults advice(Parent,Guardian,etc) to solve the problem.Just be patient inshAllah.