weird thing my friend said years ago im certain isnt true

When I was around maybe 7 years old I distinctly remember this one incident clearly. Me, my best friend at the time, and my younger brother by 2 years were sitting in my bedroom. For some reason me and my brother start play wrestling at some point, and for some weird reason I ripped my shirt off like buff men do in the movies. I'm a female.
For me, this memory is just one of those memories I personally look back on and think "well I clearly understand I did that now because I was a tomboy wanting to show off and did it in a weird way". I distinctly remember this was not a sexual thing for me at all.
However, some years went by and my friend would constantly bring the incident up saying she had personally witnessed me and my younger brother had sex ??? I remember how shocking this was at the time, and no matter how many times I recounted the events to her she was adamant that was what happened.
I don't know why this memory is coming back now, I think it's because of my lifelong OCD, but I'm worried it may be true despite all my memories telling me it was innocent. Am I disgusting?

If you know it to not be true, take comfort in that. Ultimately when someone says things about you that are not true, they are talking about a fictional version of you - an empty construct

If you are certain it isn't true, then it's not. Don't let anyone drive you crazy and think otherwise.