It’s usually the classic slowing to a stop and looking at something else (usually a mobile phone) before halted. It’s happened to me more than once.
Last time, even though I was completely stationary and the insurance initially said they would pay, once the work was finsihed they then refused.
They did pay in the end but it was stressful and I had to put that accident down on my insurance forms for 5 bloody years.
Most annoyingly even if it’s not your fault it can affect your premium if you have another accident. This is because the insurance company are b**sta*ds will consider something like your route or where you park your car or that your beahviour in some way contributes to the accident happening, ie you are a riskier bet.
Don’t want to teach you to suck eggs but if she hit your car hard enough to need a new bumper then make sure the rest of the car is thoroughly checked.
The first time it happened to I was 18. I arrived at my destination thinking it was only the bumper that was slightly damaged and then couldn’t get the boot shut due to a tiny shift forwards of the boot latch.
Chassis are surprisingly easily bent out of shape.