Unless her insurance company pays her for her damages, they're not allowed to go after the other driver for damages, because they haven't suffered a loss. If she doesn't have collision coverage, her insurance can't pay her anything.
Now, if the other driver wanted to collect 50% of their damages, because they say she was 50% at fault, then her insurance company can defend her under her liability coverage, but at best they're only going to prevent her from being liable to the other driver. They still can't pursue the other driver for damages.
I still disagree with the 50% liability call on the other insurance company's part. As an adjuster, I made plenty of comparative negligence calls, too. Liability is not in dispute in terms of proximate cause: rn_trauma had right-of-way and was traveling straight. The other driver was turning left into her path and had the duty to yield. The other driver is at fault. Where comparative negligence comes into play is if rn_trauma was doing something negligent that contributed to the accident occurring. Traveling straight through a yellow light is neither illegal nor negligent. It could be argued that if she had been going slower that she would have had more time to react, but from what I understand posted here, she still wouldn't have been able to avoid the accident.
I could see where they're coming from if they had assigned 10-20% to her, maaayybe even 30%, but no way 50%. Just, no way.
That said, is it worth it to go to court over 30-50% of property damages? Probably not. After lawyers get paid and all the time taken off work to deal with it, no.
Should she have gotten collision coverage? Hard to say. Given the age of the truck, the additional premium may not be worth it for the small chance that someone else will hit her and she'll get 50% screwed by the other driver's insurance company. It's accidents like these, where there's a dispute over liability, that cause me to keep paying for collision. But honestly, I've been driving for twenty years now and I've never filed a collision claim. With all the extra premium I've paid over those years, I could have just bought another damn truck.
It's tough to swallow BS calls like this one, but at some point you have to accept that some of that is going to happen in life and save your energy for the big ones.
Sorry to hear you're getting hosed, rn_trauma. I hope you're able to find a better, even more awesomer truck than this one was.