duplex fire in the summer, is there any liability between tenants for damage?

[Kyle Hipp]

I have an upper lower duplex in which there was a porch fire this summer. The lower tenant caused the fire in that a cigarette was the source of the fire. It was an outside covered front porch where smoking is allowed (no smoking in the property). The lower unit did not have much damage just a lottle smoke in the door, patio door and front picture window replaces. Smoke damage was the bulk of the damage inside the residence which the upper unit took the brunt of. The porch was rebuilt as well. 

It was roughly $30,000 in total damage which was a lot higher than I originally estimated but the cleaning was much more extensive than I originally thought. 

Now to my issue a couple months later. The upper tenant had renters insurance and the lower did not. The upper tenant with insurance had all her possessions professionally cleaned and she did have some issues with clothes shrinking and the insurance company was not nearly as responsive as should have been. She had a $500 deductible. She has been a great tenant for about 4 years. This property was actually my primary residence and she lived above then as well. She was a friend of my wife and still is. She is satisfied how well we have attended to the issue and got everything back together in record time and even upgraded the property for her out of our pocket in the process. 

She has inquired with me about getting her deductible reimbursed from the lower tenant. Her insurance company said this would have been reimbursed if they had had renters insurance but have not pursued collecting anything outside of that. What is your take on this. The lower tenant could have been more careful with the cigarette and used a more appropriate ashtry however I don't know if that qualifies as negligence where he would be legally liable. I am sending my insurance agent a message regarding this to get her take as well.

Thanks for reading my rambling, I like to be thorough.