TC (TurboCache) video cards use main system memory to do their graphics processing. They work great for desktop PCs that don't need any 3D, but have a very hard time with any gaming at all. It might work tolerably for Sims 2, but remember that the card will be taking 128-256MB of system RAM away from the computer so you'll need to add at least that much extra memory to your specs just to stay even...
Of the two video cards you mentioned, I would definitely take the 9600Pro. However, since the 9600Pro isn't available in PCI-E that I can can find, I would say that the 6200TC might be a reasonable option in your situation. A true 6200 with onboard memory would be dramatically faster (50% or more in most games), but it will cost you about $20 more. If you are able to squeeze out the extra few dollars, I think she would be MUCH happier with
this card than the 6200TC...
EDIT: Since you'll want to have 512MB available to play Sims 2 smoothly, you really would want to put at least another 256MB stick of RAM in the computer if you go with the 6200TC card since the card will make it so that the system only has 256MB or 384MB of RAM available (depending on whether you dedicate 128MB to the card or the full potential 256MB that the card can use). Based on that, I would say there really isn't a question and you should go with the full 6200 for $20 since another stick of ram will cost you at least that much. Of course, the final answer comes down to available budget, and if you simply can't afford it, then go with the 6200TC and the 512MB of RAM as planned and she'll probably be OK.