My best guess is that the Texas story was somehow a crucial part of her "plan" and she planned on meeting him in the baggage claim area of the airport. Didn't need security clearance; she could pretend she had just gotten off a flight. He wouldn't make the connection with the stolen baby in TN as "I just picked her up from the airport!"
In terms of the children being taken--I had and continue to have serious doubts about the mother's story. Maybe this woman did just scout out moms in the Walmart, but why, coming all the way from Alabama, did she choose that Walmart? That town? Why was the mother stabbed repeatedly, but so shallowly? Maybe it was luck, but I can GUARANTEE you that if I was mobile enough to run across the street, one or three of my children would be with me. No way in hell would I leave more children than I had to inside the home with a potentially homicidal maniac. I'd die first. That might sound like monday morning quarterbacking, but I can't imagine a single situation where they wouldn't be my first and only priority.
Her statements after the abduction bother me. I don't like to judge anyone's method of dealing with these things, but she appeared very cold. Her comments about the phone call that was made sent my radar up. She clearly wasn't dying; why would the abductor say she was? "The job is done" sounds like something she picked up from a movie.
The FBI is saying there's not an ongoing threat, yet these kids are in state custody. I'd like to believe they don't take such things lightly. I bet they apprehended the woman and her statements led them to credible information that this abduction wasn't by accident.