+1 for "forcing" your sister to use PCLOS. Since I am a Linux user who only triple boots Linux & Windows because I am a tech and need to stay up to date on all Windows software etc, it's nice to see someone introducing their friends and family to Linux. Although I prefer Debian based distros with Gnome or Xfce DE, when I do use a KDE desktop it's usually PCLinuxOS or Mint KDE. My only other suggestion as far as security in Linux would be to get her using Noscript extension as well as AdBlock Plus, whether she is in Firefox or Chromium. And as another user said, make sure her firewall is configured correctly in PCLinuxOS. As far as her Windows instal, you'll need a whole lot more security as I'm sure your aware of...lulz.