My mother is insane…

I’m the oldest of three girls. I’m getting old myself. Today I was having a phone conversation with my youngest sister (in her 40s). We grew up in a very extra home. My mom was both physically and emotionally abusive (especially to me). My dad worked a lot. But, he was a loving, good dad to us. He’s since died. Today I was telling my sister how proud I was of her. She’s had counseling and you can really tell. We fell into the conversation about growing up and how hard it was. (I should mention that I have no relationship with my mother. My sister does. My mother is ill and my sister tries very hard to make sure she navigates her illness the best she can. - my mother has remarried). Aaaanyway.. the childhood discussion touched on the topic of “can you believe she brought in a foster child!? She didn’t even like us!” My sister didn’t really remember her but I remember a few things- I was probably 10 at the time and the foster girl was a couple years older. (My sister is like 6-7 years younger than me). So anyway, my mother called my sister while she was texting and my sister asked what happened with Suzie and my mother says, “well, I walked in and found her trying to put something in your vagina, so I slapped her and had them (CPS) come get her. I was like, WHAT!?! First of all, why il would she be finding this out NOW!? Second of all, I remember Suzie leaving and it wasn’t sudden. We knew she was going and I remember specifically that a family member was taking her in so the “called CPS” thing and they took her doesn’t check out. And finally, my mother never took her to a doctor, called the police… nothing. My poor sister is told this in a random Sunday phone chat! Anyway, I feel terrible about this, my sister is freaking out, and I don’t really believe my mother. My dad isn’t alive to ask… Like I said, a very extra family life…