How do i not make this a big deal?

My older sister has taken to kissing up to my little brother in a way that may be genuine, but sometimes i feel it's not. They've got a similar type of personality, whereas i'm seen as a more fiery person who somehow manages to get herself into the strangest situation. My sister treats my younger brother like he's older than me, spends a lot of time kissing up to him, and at one point made the mistake of bitching about me to him. My brother and i were inseparable at the time, and he came straight back to me and told me what she said. My sister and i have the same talent, but she's always been threatened by the fact i was more outgoing than her. Both my brother and my sister feel like i'm my mothers favourite and i wonder if a secret resentment has sprouted from that. Maybe not. It's just that something traumatic happened to me during this past year, but i'm over it now. I was brutally aulted by my ex best friend with mental health problems, ever since i've become emotionally unstable and that outgoing spark i had began to disappear. I love my sister and she's really supportive at times. But sometimes i feel like she's become desperate to be this cool older sister. She says things to me in front of my little brother that she doesn't say to him, like calling me a or a prick. My little brother also doesn't know that when he moved out the reason my sister didn't come and visit him wasn't because she was exhausted from work, or ill, she said that she couldn't be bothered to make the journey, and he's the one that chose to move out, (she's been talking about moving out for ages,) he actually did it. Sometimes i feel like she enjoys the sense of discomfort i feel, like if were arguing she says she's going to see him to rub my nose in it. It comes out in arguments that she thinks i'm spoilt, and i have no respect for her, then she starts screaming her head off at you, to cover the fact that her arguments are often insecure and hyppocritical. In one debate she basically expressed that she feels i get in the way of my little brother letting other people in. I don't, he's very independant and makes his own judgements. How do i just not care? I don't want to make this a big deal, how do i get over these feelings that are creeping up on me? I just feel like sometimes she says something, and disguises herself to be something else?