That doesn't explain being pulled over before they have checked her documents unless they are using a licence plate scanner to ID her beforehand. Doesn't sound likely due to the questions about whether it is her car - or those questions are therefore blatent harrassment.

I'd recommend Gladwell's last book 'Talking to Strangers' about how preconceptions and cognitive biases shape our interactions and how things can quickly derail as a result. You could put a spin on their motives that it is a prejudgement of her as a person of interest - but that then becomes an issue of individual training or a systemic failure in the whole force to not let that happen.