The situation definitely doesn’t make complete sense and my heart goes out to her loved ones. I hope somehow there is a happy resolution. From what we currently know now, I can only think of one scenario that makes sense. It’s just my opinion though, of course.
Don’t think there was ever a toddler; more likely an adult or even an item that looked like a toddler that got her attention. She pulls over, gets out, and gets attacked by someone. I don’t think this person was trying to lure her, but more like while doing this, she came across someone with severe mental health issues or violent tendencies who saw her as a threat. The only thing that I’m missing is why they haven’t found her yet, but it could be a result of the terrain and other factors. There was a case in my area where a 13/14 year old boy went missing while riding his bike. Happened in a nice, safe area of town on a relatively busy main road at sunset. They didn’t find his body until the next day, but it was just off the edge of the sidewalk and had been missed multiple times by search crews and LE. The boy was just riding along and happened to come across a violent homeless drifter from down south who stabbed him. Completely random, unexpected, unprovoked, and happened on the sidewalk of a busy street. In my opinion, a situation like that makes more sense than someone purposely luring people off the side of a busy highway.