The quick approach.

As this target could cause problems, she must be converted quickly, and there's no time to dawdle with trickery. But how can the officer be made to stop her car?

Running out into the street, your nude form is immediately spotted by the female cop, who puts the police vehicle into a screeching halt and steps out of the door. The blond human doesn't stand a chance as you quickly leap onto her and maneuver your attack hand to the back of her head. You morph your index finger into a long needle and inject her at the base of her skull, sending millions of nanobots into her body. She instantly collapses and begins to moan in pleasure. The transformation from human to machine is a pleaureable experience. Within seconds her entire body becomes silver and then returns to its former color except that every blemish has been erased. She then stands up and reports "TX-3280, transformation successful. This unit is ready to proceed."

"What is your background?" you command.
"My human name was Kim Thomas. I was a 25 year old female patrol officer. I was about to end my shift and return to my home."
"Do you have any clothing with you?" you ask.
"Yes," she replies, "I have an extra uniform." You put her uniform on and you both enter the car.