If CM had a fear of being abducted , maybe she had a "feeling" something was not right when they were walking into the garage and calling her boyfriend from EA phone was kinda like a "clue" just in case something was to happen.
I totally agree with this. And her calling SN to let them know they were still walking. I think she knew he was acting off.
This is going to sound crazy, but when I used to date guys I would purposely leave my hair in their car in case something happened to me, so police would know I'd been in the car. I watch WAYYY to many murder/mystery shows.
So is the thought now that she did have her keys with her and she only wanted him to walk her to her car.