If you have comprehensive coverage on your vehicle you could make a claim under this portion of your policy. However since you only have liability you cannot use your car insurance coverage to make a claim.

You should then see if you can place a claim against the property damage liability coverage of the person that parked her smoking car next to you since it would appear that it was her fault the fire started and jumped to your vehicle. It seems from the fire investigation that it was her actions that caused the fire so she may be held liable by her insurer thus allowing them to accept your claim.

If for some reason her insurance does not find that she is liable and thus will not accept your claim then you may need to see about going after her personally since it appears that the fire investigator found her negligence in closing the hood on the speaker wire which then caused of the electrical fire. So if her insurance company denies your insurance claim for the damage from the fire that spread to your vehicle then you may want to seek legal advise and see what options you would have at that point.