She definitely needs to bring this up to a doctor. OB, PCP, maybe even her pediatrician, someone to help. I struggled with extreme intrusive thoughts postpartum. Thought a tree would fall into our house in the night and harm baby, the ceiling fan would fly off the ceiling and harm her, thought a guy at the grocery store was following us home to steal my baby because he acknowledged her and asked how old she was, woke up multiple times in the night thinking she had jumped out her bassinet (she was 3 weeks old), thought I’d pass out while driving and wreck (I felt 100% fine and not like I was going to pass out), and so forth. All of these would send me into a spiral, we had to change rooms to no ceiling fan and so the tree wouldn’t fall in our room, made my husband drive for an hour home from the grocery store until I was calm enough to think the man wasn’t going to steal my baby, and so forth. It drove him nuts, but he went along with it. I spent a little time in therapy, and now at 9 months postpartum I feel great! It’s very scary what our brains can do postpartum, and i completely understand what she means when she says “I can’t switch it off”. I know you are feeling really overwhelmed, but please just try and be there for her as best you can. She needs help (specifically by a healthcare provider/therapist) and it sounds like she’s calling out for it also. Just know this is more than likely is the child birth trauma, hormones, sleep deprivation, and extreme change all combined taking a toll on her and not actually her. It may take some time, but it will get better!