Geez, it isn't you, it's her! I experienced some pretty crazy things coming out of my mom's mouth too as an adult. She would say that something happened (about something that she did that would make her a good parent) and it didn't happen! With my mom, she doesn't see reality, she interprets reality to meet her needs.

If your mom has problems remembering discussions about sexual abuse I'm wondering if she was sexually abused? Woman who were sexually abused and never healed and are still in denial about it, deny their own children's abuse. For them to address their children's abuse, they would have to address their own and they "can't" go there. This is the classic reason why some children don't get protected and I'll bet that abusers know this.