I know some people disassociate and block out the worst traumas, but it doesn't sound at all like your experience. You mother may be doing that, or maybe she is purposely trying to convince you it didn't happen, perhaps thinking somehow that will help you.

I say trust yourself. I can't believe that someone would make such a thing up in their own mind, it is too painful.

Pandora's box is really tough. But it has to be faced at some point for any real chance of a cure. IMHO, anyway.