I can understand her feelings of frustration. I suppose the "warning" is good even for those who have or have not had bad experiences buying a personal sale second-hand.
I've been burned in the past by sellers who didn't deliver on their end, and/or were unwilling to help the customer out in SOME way when foibles happen. Most of my experiences buying from people have been good, and it's been a trustworthy, drama-free experience. Most people do just want to offload their extras and recoup some cost, but some don't want to be bothered with making it a good deal.
I'd be a bit on the ranty side too if I had the same experienced with a pre-owned digital device. I would want the slate wiped clean and anything associated with it to be all mine.