From what I have done in the past, the only real 'work' that the machine will do is take the RAW data that is captured and compress it so that it will fit on a DVD, unless she is going to display hours of work, only moderate compression will be necessary. Now, if you're looking into displaying videos at 'high' resolutions 1024x768, using proc intensive programs like Combustion, or using programs like 3d Studio, LightWave or Maya to do CG effects, the machine that you had quoted will do a whole lot more than necessary.
I know there will be someone out that that will tell you that an Athlon with a Gig of ram will do VERY well for this.
With the speeds of SATA and the speed of drives now adays I highly doubt that a RAID will be inorder. I could almost say that a 800$ computer off the shelf from Best Buy would do what she would need, though a hand built one would always be better.
From what I've heard so far, an average machine purchased today would do her well. Just make sure that you make this machine dummy-proof, figure out what she wants to do. Mainly, you will be looking for automated software that will allow her to join videos, and have fading/transitioning/wiping that will allow her to seam clips together. Same goes for the encoding and burning. Make sure that you can find some software that will do what she needs, without being overly techical.
Also, remember that the chain is only as strong as the weakest link; If she tries to get a $250 camcorder and edit clips together on a $1500 machine she won't get the quality that she is looking for.
Now, mind you, I have had a hard time saying this... ...and I only say this rarely. I have to bite my tongue when I say this to.
If she is not computer literate, wants to be able to do this easily and doesn't want to spend a great deal of money... ...Buy a Mac.
Yes, I said it. Laugh all you want! But if the person who will be doing a great deal of the work just doesn't want to learn, or is terminally computer illiterate, steer them toward a Mac.
< phew > Wasn't as hard as I thought it'd be.
-SF