So the adjuster lady at geico seems to be the last person to make a decision on this and she put my wife at 100% fault over this accident (after Geico apparently gave it to me in writing that she was not at fault when she picked up the fixed car from body shop and we didnt pay the deductible). I dont agree with Geico and would like to fight it, but apparently she’s the sole decision-maker on this claim she said. What are my options here?

1. Can I get a lawyer and should I get one? And would it be worth it?
2. My insurance premiums are about to double up right?
3. My blood is boiling thinking why she did not even try to find my wife at at-least a partial fault instead of fully at fault here given she did everything by the book IMO. Pls correct me if wrong, but be gentle pls.
4. We're in California

Edit : Geico said, he was not more than 10 MPH over the speed and its legal for him. To which I tried to counter that he was speeding much more than that as i found from various online tools.

Has someone been in a similar situation recently ? What have you chosen to do?
Should I get a lawyer? Is it worth the time?