The unnamed woman was dangling out of the vehicle on the M25 motorway south of London, Surrey Police wrote on Twitter.
“It is only by luck she wasn’t seriously injured or killed,” they said.
They posted a picture of the open passenger window, alongside the hashtag #nowords.
Asked by a user if officers explained the dangers of the attempt to the woman, the police replied: “Every chance they worked it out before we spoke to them about it!”
Researchers found that the most selfie deaths occurred in India, followed by Russia, the US and Pakistan. Most of the victims were men (about 72%) and under the age of 30.