About sudden onset dementia - this is what happened to my mom right in front of me and it's terrifying. There are many medical reasons for it I'm sure, and I'll spare the long details, but in my experience & opinion this is next to impossible. And looking back there were small signs - which is completely opposed to how sharp Cheryl was. The stealth required to plant animal blood with no animal or container nearby, avoid all cams, avoid attracting any public attention with the related confusion, lose said animal or container along with phone, wallet & keys which are never found, end up at the culvert, walk against the current to hide on the east side, place a bag over her head in the rushing cold water & force herself to suffocate & drown is NOT consistent with dementia. Wandering into a nearby park & falling into a creek, or walking in front of someone's car, or attracting attention by being disoriented, that I would believe.
As for the animal blood, that sticks with me. I seriously doubt it was in the car the night before if it was fresh & of quantity enough to smear the next day. Not dried or congealed. I also seriously doubt that Cheryl got a new cat who sounds like a skittish rescue of sorts and immediately during the week of transition decided to change the cat's diet. That can be really difficult & make them sick. And to change it to raw hunted meat, not store bought, have that much blood in cat food meat leaking from the package only on the passenger floorboard, then to disappear, never heard of before or since? With Cheryl not even discussing that drastic of a dietary change with her friend & cat rescue/breeder or her husband? Not buying the cat food angle at all.