If my mum is playing child favouritism, why can't she just abandon me? Clearly, my younger sister is favourite?

when my younger sister buys clothes, she shows them off to my mum and my mum always says how nice they are and how she's becoming a lady, with me, when I buy something, I tend to never tell her but she knows when I buy something, she always asks "is that new?" I reply "yes, it is", and then she says "well, it doesn't suit you". When people say they think I've lost weight, my mum always says "well, people say you look like you've lost weight, but I can see bulges on your waist". If she insults me like that, clearly she doesn't care about me, so why can't she just chuck me out of the streets. These are just a couple of examples, there are plenty more where she looks at my weak points and insults me. I hate jealousy, if she's jealous of me, she's not a good mother at all, so what's the point of raising a child if you're a bad, insecure mother?