what multiplier should I use when negotiating with an insurance co for post concussive syndrome?

I was in an accident that 100% the other person fault. She ran a red light and I hit her. I was not speeding, obeying all traffic laws and I just could not stop in time. My car was totalled. I was taken to the hospital and diagnosed with soft tissue injury to neck and back. I had severe headaches from that day forward, but was advised it was ok to return to work. After about 2 weeks of work, I was told to take time off as I was diagnosised with a concussion as well as post concussive syndrome. I was better after the two weeks and returned to work. The only residual I had was some minor memory loss. Since that time, my memory has deteriorated to the point there are many conversations I have no memory of whatsoever and some I have minor recall, but fuzzy. My doctor sent me for an MRI to ensure there was no structural damage and that was normal. I am waiting to see a neurologist. My question....if the insured has a $100,000 limit on her insurance, am I ok to settle, or should I wait? Also, looking around on the internet, I am seeing articles about multipliers from 1.5-5 to be used depending on the severity of the accident when negotiating with the insurance company. WHat would the severity of this type of injury warrent in the way of a multiplier? Thank you for your time an consideration.