We've followed your suggested steps - but it din't help at all, sadly. I guess at this point we're runing out of options?
After work I'm going to have her PC scanned by anti-malware software, maybe there's something hidden on her PC which makes it unable to run TERA and VPNs (it still bothers me that they didn't want to launch). And we'll install some proper antivirus... But I honestly don't know what else should we do. Call technical support?