Never been able to get over this

well when i was like 10 and my sister 11 she wold have me and my younger sister "experiment" sexual things like making out and actual sex. at first i was willing but i felt wrong about it. so one day i punch her in the vagina and walk out. that was the end of that. but ever since then i can't let go of it. I don't trust her. I have reservations about her We never talked about it and i don't think i ever could. We were both wrong. Worst part is everyone looks at me crazy when i don't act all loving towards her, if only they knew. Of course there are other reasons i don't liker her but i think that is the main reasons. Idk im trying to get passed it.