Rob...

It sounds like she has her mind made up, but you might want to ask her if she honestly believes everything that she reads and hears in the media without question. If the answer is "no" then why is this any different and to be believed without question or any research on her part as to whether or not it's actually documented to be true (documented actual problems directly attributable to low carbing, not "might cause" or "could possibly cause" or "we think it may cause")?
Sure, the media says a lot of negative things about low carbing (most of it based on very poor research, if any at all), but the fact is that the medical profession has been challenged to, and has yet to produce, one person who has developed kidney disease as a direct result of following a low carb lifestyle. Of all the negative stuff I have read regarding a low carb WOE, all of it has been based on opinion instead of fact or by quoting a study that was based on a high carb diet, not a low carb one. The actual studies that have been done on low carb have failed to prove the dire health predictions as outcome to be so, much to the surprise of some of the researchers. Quite the opposite in fact. Weight loss comparisons aside, the blood studies of the low carbers looked better than the control diet participants' in every study so far at the completion of the study. As a matter of fact, I work with someone who is prone to kidney stones and has had them several times. He's been low carbing for about 18 months now, has reached and maintained his goal weight and has yet to develop a kidney stone. I myself have been following a low carb WOE for 2+ years and as a diabetic have blood studies done every 6 months (which include kidney and liver function) and so far none of my organs have failed, exploded or othewise shown any sign of problems. This is significant since diabetics are prone to such problems (kidney disease) just by having the disease, let alone by adding low carbing to the mix. If it in fact does cause such problems, I'd think they would have begun to show themselves in my blood studies by now if they were going to. Not long term enough? Dr. Atkins followed his own WOE for many years without health issues and Dr. Richard Bernstein is now 40+ years into a low carb lifestyle without ill effect (just the opposite in fact) and he is a type 1 diabetic...even more prone to heart and kidney problems just by being diabetic. Not only has he not developed any of these problems, he reversed his already existing kidney disease by low carbing along with several other diabetic complications that he had already developed before he began low carbing.