There are two sites I'd recommend: www.stumptuous.com/weights.html and www.exrx.net.

I'm no expert, but I do use the machines at my gym.
They are usually grouped according to muscle groups. For instance, the machines that work your back muscles are in one area, while the machines that work your chest are in a different area.
Usually each machine has a sign on it that explains which muscles it works and how to use it. But, I'm glad that she'll get some direction, because it can be very overwhelming at first, and she needs to know how to adjust each machine for her height. Plus, she'll learn how to use the machine properly for good results and to avoid injury.
Good Luck!

Funnigrrl you beat me to the sites I was going to recommend, those two sites are awesome....... Dill it's a very good idea that your mother get instruction and training on the machines......

Thanks guys!