Something to remember is Linux is pretty much Linux, just some versions are harder to use than others, some are prettier than others, some are made for older hardware, etc. So it depends what you need and want.
There are two main desktops. Gnome and KDE. Gnome isn't ugly or anything, but KDE at times looks better than even Windows does. And with eye candy comes needing decent hardware to run it.
Some easy point-and-click ones I've used lately are PCLOS, Mint, Puppy (small but good!), Mandriva, AntiX, Crunchbang. My old laptop barely ran Mandriva. Looks good, though.
I've used all of the above with basically never needing to type in a command line for anything. Some people like to use versions of Linux with total control, command terminal lines and all that, while other people just want something plug-and-play that works.
The best part of most Linux versions is you can put them on a thumb drive or CD and boot from that to test them out until you find one that fits you the best. Your mom could try half a dozen different ones and choose from those.