Especially, the operating system..Windows XP? Windows 2000? Windows 98?
I suspect that there may be spyware or malware on the computer and it's caused damage.. Does she have antivirus and antispyware tools installed on the computer? Does she keep them up to date and run scans with them? If not, you'll need to install such and run them.
If her user profile is corrupt, there are ways to use other usernames, or to create a new one.. She'll need to log in as a user with administrative priveleges in order to make any serious changes. (When ready, If she's using XP HOME, then restart the computer to "Safe Mode" using the instructions in the link below. You'll be able to see a "Hidden" user listed as "Administrator". If the default hasn't been changed, there will no password set for that particular user name.. Leave the password blank, press the "Enter" key and you'll be able to use the "administrator" log in to make any changes needed.)
The internet access shouldn't be an issue for any user on the computer although a "temp" user may have limitations I'm not aware of. Likewise, although the screen saver is probably "there", because she's logged on to a new user, it won't show up automatically because she's using a different profile..
We need lots more information and although we will try to help, you may need to get someone sitting at the computer that has some experience fixing them.
Hope this helps.