I don't like my autistic sister who I only found out recently has autism
Why don't you like your autistic sister?
She's always yelling around, sometimes she never stops talking.
People with Autism can't always control what they do or how they act. You should try being more understanding of their condition and supportive.
I'd rather have another sister instead of her.
Not everyone can pick their siblings but you have a choice to support them or not. Wouldn't it be better if you two got along? She'd be better off having someone to help her deal with how she acts socially.