Are there cameras going from where her car was found back towards her house & then to the culvert??
Here's my thoughts, take it for what it's worth [emoji16]
She left the house, then realized she didn't grab her badge, she pulls over, where her car was found to text her carpool friend, she sees someone she knows or someone she had planned to meet & IF she wouldn't have forgotten her badge would've had time to talk with while waiting for carpool to show up, maybe. "Person" gets in the car with her so they could talk, she tells "person" that she needs to return home to get her badge, her phone dings because carpool is texting her back saying she'll wait, it may irritate "person" so she then turns her own phone off in order to give "person" her attention, they start heading towards her house (not sure if cameras in the area that may have caught her/them on video) but something happens on the way to her house, maybe "person" says something that makes her feel uneasy or in fear so she pulled over & told tells them to get out, Idk, then "person" puts Cheryl in the passenger seat & starts heading towards somewhere not knowing where exactly they were going to get rid of her, they see the culvert & think this is as good a place as any; so person pulls in & gets her outta the car & into the culvert then heads back to the park n ride area, not because they were worried about where Cheryl's car would be found but because that is where "person's" own vehicle is or they needed to get back to the transit station area to get to work, they either get back in their vehicle, a bus or their own carpool or could've just walked away. It'd almost be perfect except "person" didn't expect there to be blood because "person" choked her to death in order for them not to get messy before work, but for whatever reason she bled, maybe the cuts on her fingers are from her grabbing the car door handle trying to get out & away, then after "person" switches seats the cuts bleed out, causing blood to be on passenger side of the car, idk what size the cuts were or if they were big enough to cause that much blood loss, but they had to be significant enough in size for ME to mention them imo.
I know there are holes in certain spots but I'm sure y'all get the idea.
The thoughts & opinions stated above are that, MY random thoughts & opinions.