How many times have you clicked the OK button before giving up?
Has your mother ever herself published any photos to anywhere (Facebook/Flickr etc)?
What happens if the Mac can't see the Internet and you launch iPhoto? (ie unplug the ethernet cable or turn off the Mac's Airport)
If you can get it to realise it shouldn't bother sending anything out to the 'net, then maybe it'll start up and you can delete any "Shared" Facebook/Flickr albums the kids might have created (they're listed near the bottom of the left hand panel in iPhoto).