The first thing I would try is LAA, Large Address Aware. It's a little program that allows caw to use up to 4 gigs of ram, instead of the 2gigs it's programed to use. In your friends case, it will be able to access all 3 gigs she has available.
LAA
Download here: http://www.techpowerup.com/forums/showthread.php?t=112556
Read about it here: http://simswiki.info/wiki.php?title=Sims_3:Large_Address_Aware
Any other caw issues, check out this thread: http://www.modthesims.info/showthread.php?t=441595
Also, she/he probably already does this, but shut down any other programs while running Caw. Open up the task manager and look at what programs are useing a lot of memory.
This is what mine looks like right now, I could shut down firefox, skype,Side bar, and probably Origins (as long as caw doesn't need that to run EIG. I don't think it does.)
