my sister had sex with the guy i was in love with

my older sister (22) had sex with my best friend. I was in love with him for about a year and he was there for me through everything. I don’t know what to think about this, but she close friends told me that they had slept together, and i confronted them both. They both lied, and a few hours later my sister came clean saying “i didn’t think it would be that big of a deal.” “you weren’t dating him” “i didn’t know you liked him”

let me remind you, i talked about him CONSTANTLY. Anyone and everyone could tell how I felt about him. It was public knowledge. He knew I liked him. He would tell me “it’s not the right time for us, maybe someday” and he would lead me on constantly. Then he fucks my sister. Great best friend & greatest sister! I just cut him out of my life, but I’m not sure what to do about my sister. Any help?

update: no idea how a lot of you think i shouldn’t cut her out of my life. I cut her out of my life because of how toxic she is. Just because she’s my sister, doesn’t mean I need to keep her in my life. She has mentally AND physically abused me for years. you don’t need to keep someone in your life just because “they’re family” if they treat you bad and hurt you cut them out.