Certified Coverage specialist.
She has been in the car/home/health/life/etc insurance for the last 21 years.
This is the first time she has ever heard partial assesment of blame by insurance.
First off, is your state a No-Fault State? If it is, they can't do that.
Second, ask them what law they are using to get around your coverage. Please ask for the proof they used to assess this.
Third, get the police report. Go over it, with possible, with the officer that wrote it. Verify what he/she wrote.
After you do this, ask an Attorney to review your situation to see if they think anything is a miss. Most attorneys will do this for a small charge or none at all.
Good luck.