Chrome (and Chrome alone) cannot access the Internet

I would recommend trying turning the firewall off, and make sure she hasn't got any other non Windows firewalls installed. Then see if it works, if it doesn't you at least know it's not down to the Firewall itself. If it is then you have a new line of enquiry... You could also try doing a reboot with non-Microsoft services objects are disabled as well as a selective startup disabling startup items. This should rule out any background processes causing you grief.

Personally, if you don't want to waste too much time on it, I would consider installing Firefox on the machine for her instead of Chrome, I know it's not a solution, but it is a lot better than forcing her to use Internet Explorer.

EDIT

Thanks for clarifying that, I can suggest one more thing, but it might not be the most useful suggestion, using procmon you could check to see what Chrome is actually doing when requesting pages, because from the sounds of it is doing something it shouldn't be. But since this will show you a lot of information it could take you a while to figure anything useful out. I would at this point refer back to my previous response "replace it with Firefox"... Good luck!