This is a very good point. As far as the legal ramafications are concerned, a repair like this is so important to the safety of the vehicle, if you DO perform it, I would seriously consider having her sign a legal waiver of litigation if she were to get into an accident and the structural integrity of the roof is diminished in any way. It may not be a roll over, either. A strong frontal impact is absorbed through the A-pillars and front door frames on in through the roof as well.

She should be completely aware, in writing, that she is taking the car knowing there are risks. And, to protect yourself, it should be put into writing that she waives the right to file a lawsuit against you.

No matter how much confidence you have in your own work, and I'm sure you can do a good job as you seem like you are willing to go out of your way to help her. I'm just pointing out down the road what could happen..... and when she goes to sell the car, if there is nothing in writing, and someone else gets into an accident and finds out after the fact that the roof was replaced, they could come after her.

Sorry to put the damper on the perverbial parade, but I'm involved in a lawsuit of my own (plaintiff, not defendant), and through my case and lots of legal research done on my own I've learned to think like a lawyer at times.