I have shot a 243 for years and never had one go more than a few yards. I have seen deer take a good hit from a 270, 7mm Rem Mag, 25-06, 30-06, and 30-30 and keep going. Anything to do with the cartridge? Probably not. It happens. I can understand your concern with the 243 but I will just about bet that she was using 85 grain Remington Corelokts which are pretty much crap. The 243 will do a job on deer without a doubt if the shooter does their job which includes using the right ammo for the job. I will agree though that a 260 or 7mm-08 make a better deer rifle, especially for a novice hunter.