In the beginning, when she escapes from the cult, she is found by one of the cult guys (Watts?) at the truck stop, but he lets her go, and the sister can drive three hours to get her. Why didn't the guy force her to return? It's the same guy who follows them in the car at the end.
shareHe let her go because he couldn't risk police intervention. When he grabbed her arm, Martha resisted a little. What if she started screaming and making a scene? There would be witnesses, someone would call the cops, then there would be an inquiry, which would lead to an investigation, which could expose the entire cult.
share[deleted]
For reasons stated by the first reply, and also as we see in the end, they never really "let her go" -- they are going to hunt her down; they're just biding their time, but they will always be seeking her and now that guy is following her right home to the city too.
share