When an teenager becomes insecure about her boyfriend’s friendship with their female road-trip companion, she decides to make him jealous by inviting a dangerous hitchhiker along for the ride.

I think you meant-

Jealous of her boyfriend's association with their female road trip companion, an insecure teenager invites a hitchhiker who turns out to be a serial killer

Agree with mrliteral.

I look askance at stories where the inciting incident or a major plot pivot depends on a character doing something that's just plain stupid, that doesn't make sense.?

How does she know that picking up a sinister stranger will make her boyfriend jealous?? Make him anxious, worried -- oh, yeah.? But jealous??

?

Agree with mrliteral.

I look askance at stories where the inciting incident or a major plot pivot depends on a character doing something that's just plain stupid, that doesn't make sense.?

How does she know that picking up a sinister stranger will make her boyfriend jealous?? Make him anxious, worried -- oh, yeah.? But jealous??

?