I’m thinking that you probably didn’t set a password at all. So after auto-login — no need to do the live USB thing — just set a password for her account…
passwd
# Enter the password here. It will ask you to confirm.
After this, sudo should work.
And as for…
It’s probably broken now, so see this tutorial…
However, this is really a separate issue, so if you need more help with that machine, then please start a new thread.
