Take the hard drive out of her old computer and put it into her new one. Drag and drop the data folders to the new hard drive and remove the old drive again (or just leave the old hard drive there as additional storage).
If she uses Outlook Express as her mail program, download this program and install it on the old computer before removing the hard disk: click here
It has a free 30-day trial.
Use it to back up all her emails, address book etc.
When you have moved the hard disk, install it again, but on the new hard drive and restore all the emails etc.