** Trigger Warning**
I can relate very closely to your situation. I have a similar guilt till date and maybe it has started to fade away when I discussed this with my T. But I dont know. Here is my story:
I was 10 at that time(before my CSA ) and one night I was sleeping beside my sister(she was 12 at that time). I randomly woke up during the night and out of curiosity slipped my hands in her pants and felt her vagina. I did that 2-3 times. I remember that I was just curious. After that I did something very horrible, which I have no explanation for - i took some spit out of my mouth and put into hers. This sounds very weird and am very ashamed to why I did it. I have no reason why I did it. After that I just kept laying and couldn't sleep. After an hour, my sister woke up and she asked me to lay on top of her. I did that. I asked her back to lay on top of me. All clothed. We did that a couple of times. That was it. Next day we briefly talked about it and never discussed it again.
This incident changed my whole life. I felt an enormous shame and guilt inside me from the next day on. I have been super nice to my sister and all other girls I have ever met. I discussed this with my T, and she said it was due to curiosity. I understand this in my head, but my heart still doesn't understand. Another thing that I am worried is whether I affected her life as someone else affected mine. This almost breaks my heart. I don't know what to do, only thing I do is being nice to her and to other people, so I don't break any more hearts.