Allstate is saying im 30% at fault for a rear-end collision where i was stopped at a red light. Anyone fought a comparative fault assignment like this?

I got rear-ended on April 18th sitting at a red light on a four lane road in suburban Atlanta. The other driver hit me at maybe 35 mph, pushed my Civic into the crosswalk. Police came, did the report, listed her as fully at fault. She admitted to looking at her phone in her statement.

Three weeks ago her insurer (Allstate) sends me a letter saying their investigation determined im 30% comparatively at fault because my brake lights were "non functional at the time of the impact" per their inspection of my totaled car at the salvage yard. They are reducing the settlement on my injury claim and the rental coverage by 30%.

Here is the thing. My brake lights worked fine the morning of the accident, i have a dashcam clip from earlier that day showing them on. The salvage yard inspection happened 11 days after the wreck, after the rear of the car was crushed and the entire wiring harness was destroyed in the collision. How are they saying with a straight face that crushed brake lights prove they werent working before impact?

I have a police report listing her as 100% at fault, a dashcam from earlier the same day, and obviously the rear of the car got destroyed in the crash. My attorney says we should formally reject the comparative fault finding and threaten suit but i want to know if anyone has actually beat one of these. Is this a normal tactic or am i being singled out somehow?