Hmmm, interesting that a Whole Foods salesperson might be considered an authority on a health topic. For anyone even remotely considering using canola oil, I recommend first reading this 2002 article from the Weston A. Price Foundation, written by Sally Fallon and Mary Enig, Ph.D., the respected lipids researcher:
http://www.westonaprice.org/know-your-fats/the-great-con-olaRemember, too, that any delicate plant oil that's sitting on a shelf in a nice clear bottle is damaged. Aside from damage incurred from processing, being exposed to light is detrimental to both the omega-3s and the 6s.
You can validate your sister's own previous conclusions by letting her know that olive oil, coconut oil, and butter and ghee are her best cooking choices, the first two at low to medium temperatures, only. Ghee, especially, is great for higher temperature sauteeing. She may perhaps be interested in reading Mary Enig's
Know Your Fats. You, too, if you haven't already read it.
