Insurance companies:
1) Typically rate your risk with a statistically computed combination of comparing you to people of similar characteristics (age, gender, location, etc) and your past history.*
2) Their charge is generally driven by both their best estimate of your risk and the amount to fix any damage in a claim.
The cost of fixing damage to (or caused by) a car is always going up, same as all other goods and services go steadily up due to inflation. Therefore, even if your risk is assessed exactly the same as before, constantly rising potential damage costs would dictate an increase in charges.
* A new twist is telematics, where your detailed driving habits (roads you use, mileage, time of day, speeds you go, how hard you brake, etc) can also be used in the rating.
If your girlfriend thinks she's that much safer than everyone else, she could try this. It might say she drives a lot like others in her demographic. But it might say she's safer and deserves a lower rate, too.