I don't think lava meant "turning around" literally. Just that CD would have turned right onto 58th and gone through that neighborhood to start winding her way through the streets to get back home.
To me that says that Cheryl suddenly realized "Crap! I forgot my badge again!" (didn't even have to look to know that) and so she knew she'd return home to get it. She would have turned right on 58th and pulled over pretty much as soon as she could to text her carpool friend. And from there...I just don't know why she didn't put the car into "drive" and keep heading towards home.
In this scenario, I just don't see a single reason for her to think she'd be stopped any longer than to just send a text.
Again, it was pretty dark outside at that time of morning, and overcast to boot, so I have to surmise that whoever hurt Cheryl came at her in a surprising way. That leads me to think that it wasn't someone she knew because they would have had no reason to think she wouldn't be heading directly to the park-n-ride lot. The most logical thing is that she pulled over to text and a stranger engaged her, or she engaged with a stranger.