The point being, once you can correctly identify what ails your computer, one is way ahead of the game. Because you can google the "system tool 2.20 infection" and get pages and pages of various removal tools.
So for chuckles and grins I did just that, and just clicked om one random link.
http://www.cleanpcguide.com/remove-system-tool-2-20-how-to-remove-system-tool-2-20/
Which claims spyware doctor can do as well as hitman, and I am somewhat willing to bet further search would find removal tools not linked to any specific programs that can do the job even better.
But OP, don't let grass grow under your feet, system tools 2.20 disables your GF's entire
security defenses, and if she continues to access the internet while all her computer security fails to function, she can catch all forms of very hard to identify malware that
makes system tools mild in comparison.