For me, it's just a feeling that she is (or at least was for a time) alive. Maybe because of her dad's statements?
When I think about all we have learned about Mollie and how well-loved she was by (apparently) most everyone, I don't see how she could have been involuntarily taken while jogging. I think she would have fought like a wild woman, and made enough noise that someone would have heard. That leaves the probability that she knew her abductor, but did not realize his feelings were stronger (or just different) than hers. I think she willingly got in the car, and was taken away. I don't know if it was someone who asked her to grab a bite to eat, or go for a drink, or can you help me with my online class, etc. But she took the bait and who knows what happened after that. Normally I would think she was deceased, but for reasons I can't explain, I'm not sure she is.
That's my reasoning FWIW