The problem here is Dell should have made it clearer that Linux was probably not for her - simple test: "Have you heard of Linux?" No? Then it's not for you.
The fact is that Linux is not suited to the vast majority of computer users out there. I've used quite a few of the distros out there over the last 14 years and none of them were to my taste for a personal OS, mainly because of hardware problems. On a professional level, I develop applications primarily for Windows so it's not a good fit here either.
Most people just want a computer to work and they want it to look like every other computer they've ever used. They also want to be able to stick in a CD from their ISP and have the CD run and configure their network settings for them. That is not an unreasonable request; I know very little about dentistry, fund management, PR, or journalism, why should those people have to know anything about system administration?
Some of the other directors in my company use Linux on their desktop machines because they are technically proficient and they dislike spending money on Microsoft licences. This all works great until I send them Word docs and OpenOffice messes up the formatting when they make an edit and resave. Linux has a long way to go to overcome these problems and get onto the desktop of anyone other than a few hobbyists and fan-boys.