So if you’ve nothing to hide, you’ve nothing to fear? This cop is plainly using her power to search as a threat, openly admitting that she can’t use anything she can find but she plainly regards the threat that “you can be pulled out of the car and I can search you if you really want” as a tool to compel compliance with her “voluntary” interrogation. If she’s using it as a threat, any claim that no harm is done by the search is entirely specious. She’s not threatening to search them so much as she’s threatening to humiliate and demean them under color of authority.
If you’ve nothing to hide?