@MrGallant
She’s saying that if the Head Doctor is your target, then his stand will activate and rip you apart in your attempts to get to him, but if you are after something else, then the stand won’t activate, and you can run into the Head Doctor without fear of danger.
In this case, Josuke’s changed his focus from getting the Head Doctor I order to get the Rokataka fruit, to getting the medicine for his mom, which just happens to be held by the Head doctor.