Cd player not working

If every CD she tries gets the same error the simplest solution maybe to get her a new player.

Faulty Unit, radio and CD are full intergrated

most common cause is a dirty or bad optical pickup in the unit, it may be able to be cleaned but more common is the pickup is bad.

You listed this in the auto section, so I'm not sure just where you have the problem. When you receive an error like this and you've tried several disks with the same result it means your CD player is bad and must be replaced.

First try this,use a old cd,press and hold eject,try to insert gently under stuck cd
DO NOT PUSH FULLY IN,just lift stuck cd slightly
Keep trying this usually clicks release micro switch and works on all single cd players
If this does not work you could remove unit, and get your local auto electrician to check it out
Go to fitaudio.com for removal details,which is quite easy to remove

E20 : Focus Error Cause(s): The CD player cannot focus on the disc or there is an internal focus problem. Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If the problem is not corrected, service the unit at an ACDelco Service Center.Information provided by http://www.carforums.net/showthread.php?t=11338

E20: Focus Error
Cause(s): The CD player cannot focus on the disc or there is an internal focus problem.
Correction(s): Try cleaning the disc or using a new disc. Make sure the disc is loaded correctly. The road could be too rough or there is too much humidity. If the problem is not corrected, service the unit at an ACDelco(R) Service Center

I believe error 20 is a laser focus error, if all discs don't work unit will need repair or replacing (most likely replace due to repair cost)

The laser light is out of focus and that is why it will not play cd's you might have to replace are take to the dealer to fix that problem they have the proper tools

you need to have your player cleaned it sounds like a dirty lense