I saw this report initially on the news (I'm originally from Washington State and have a stepbrother that lives in NW WA not far from the park) The car was a rental. From the mother's interview she flew into Port Angeles from St Louis to go "camping".
There are no commercial flights into Port Angeles. It's really never had anything more than some unscheduled charter service (which would be extremely expensive for most of us). So she would have flown into SeaTac and driven or driven/taken the ferry.
Where did she rent the car from and from whom?
I have a feeling she wasn't experienced camping in this kind of environment. Any online research will warn you that the road to the trailhead where the car was found closes pretty regularly due to early snow in November, and it's a VERY wet cold season. The coat she had on in the photo would not offer any real protection, unless she picked up some heavier rain gear to supplement that at WalMart. Her footwear also, from the photo, does not look adequate for hiking, especially in very slippery (from the rain) rough terrain. Did she buy boots in addition to other things she'd need for that weather (tent, cold weight sleeping bag, heat/fire source, etc?) Hopefully LE can get a list of what she purchased at WalMart for supplies. With temps in the upper 40's in the day, and 30's at night with winter rain foreset weather, hypothermia is a real risk that time of year.
https://www.accuweather.com/en/us/port-angeles/98362/november-weather/336342
If the weather had been forecast to be nice (WA can
occassionally see some late arrivals of winter weather), there are some camping spots.
Sol Duc Hot Springs Resort Campground, Olympic National Park - Recreation.gov.
But a look at the historical NOAA radar shows the park area was seeing scattered snow flurries from the date she was seen shopping onward.
Radar Data
As to the maintenance worker checklist - it sounds like that person is not a suspect but it's odd certainly. Could she have been interested in obtaining a job as a season trail maintenance worker and got a copy of the checklist by way of introduction to the duties of said position? (there are jobs for it open at USAjobs) At her age, she might have been interested in such a position, I can't think of any other easily explained reason for the checklist.
I recall seeing an unverified reports that her 'equipment was found in the car". May have been a comment on social media though.